Archie served as the secondary antagonist in 2008 and the main antagonist in 2009.
Archie is visited by his estranged daughter, Ronnie Mitchell, whom he has not seen for 15 years, and sister-in-law, Peggy, as they are looking for his other daughter, Roxy, who has disappeared after discovering she is pregnant. Peggy knows that Roxy is staying with Archie in Dorset but does not tell Ronnie, worried that she will refuse to go. Ronnie is furious to see her father, wanting nothing to do with him. Archie and Peggy catch up and he tells her he has survived cancer. Ronnie had given birth at the age of 14 to a daughter, Amy, fathered by Joel Reynolds, but Archie had Amy immediately put up for adoption. Archie then fabricates a story that the child had died 13 years ago, though Ronnie does not believe him. Roxy agrees to return to London if Ronnie and Archie make up, but Ronnie whispers in her father's ear that she will kiss his gravestone when he's dead. Archie persuades Peggy to start a relationship while they can and tells Ronnie he will see her in London in a few weeks.
Now engaged, Archie and Peggy return to The Queen Victoria public house. Ronnie tries to tell the family that Archie is evil, but only succeeds in turning them against her. At a family meal, Peggy's son Phil argues with his son Ben and reveals the abuse he suffered from his father - Eric. Archie calms him down by telling him of his own abuse at the hands of his own father and that Eric loved another woman. Peggy realises she cannot trust him and tests him by sending texts from Suzy Branning's mobile but he postpones the wedding when he finds out. He begins controlling his daughters by persuading Danielle Jones to steal a letter from Joel that he later burns in front of Ronnie. He makes his dislike of Roxy's boyfriend, Sean Slater, clear – feeling that he's not good enough. He causes trouble by manipulating both of them and stops Sean being there when Roxy gave birth to her daughter, Amy - prematurely - by deliberately failing to phone him when Roxy goes into labour. He also controls Peggy, changing how she dresses and distancing her from her friends. Worried about her daughter's paternity, Roxy has a DNA test done and Archie finds the results, discovering that Amy's father is actually Ronnie's boyfriend, Jack Branning. On catching Suzy stealing from the Mitchells' safe, he tells her he will keep quiet providing she makes sure Sean finds the DNA test results, proving that he is not the father. This act leads to Sean kidnapping Amy, and trying to drown her, Roxy and himself, before he is stopped by Ronnie and Jack. Afterwards, Sean flees - his marriage to Roxy ruined. The discovery also leads to a huge falling out between Ronnie and Roxy, and between her and Jack, but they later reconcile.
Archie realizes that Danielle is Ronnie's daughter when he sees her locket and recognizes it as the one Ronnie gave her baby before giving her up for adoption. Danielle admits to him that she came to Walford to find Ronnie, get to know her and tell her who she was, but she has pushed her away and can't get close to anyone (unknown to Danielle, due to her guilt of giving her away). Archie realizes that he will be disowned from the family when they find out he lied to Ronnie about her daughter so he tells her that Ronnie suffers from depression and to let him tell Ronnie that Danielle is her daughter when the time is right, wanting to protect himself from Ronnie finding out about his lies. He tells Danielle that he will tell Ronnie but later contemplates strangling her. Unable to go through with it, he leaves Danielle heartbroken by telling her Ronnie knows and wants nothing to do with her, and has actually paid her to leave. On his wedding day, Archie is angered by Peggy's decision not to wear the suit he chose for her. When challenged by Peggy at the altar, he decides he loves her regardless and the ceremony proceeds. At the reception, Ronnie sees Danielle about to snatch Amy and she tells her the truth. Danielle realises Archie has lied to her but Archie claims Danielle is mentally ill. Danielle tries to prove herself but Ronnie believes Archie and throws Danielle out, later finding the locket. Realising Danielle has told the truth, she goes after her despite Archie's attempts to stop her, disgusted by his lies. Peggy is equally disgusted and tells their guests to leave. Archie's schemes and lies are revealed and the Mitchells are stunned by the news that Danielle is a relative, and that Archie is as evil as Ronnie always claimed. As the family confronts Archie for his deceit, Ronnie rushes to find and reconcile with Danielle. However, she ends up witnessing Danielle being struck by Peggy's stepdaughter Janine Butcher in her car; Danielle dies in Ronnie's arms, leaving Ronnie broken-hearted as Archie had robbed her of a life with her daughter. After Ronnie prevents her father from visiting Danielle at the morgue and then attending at her funeral, Archie is thrown out of The Queen Vic and disowned by his family - with Roxy also turning on her father for ruining her sister's life. Peggy, wanting justice for Ronnie and Danielle, orders Phil to kill Archie - so he kidnaps him and threatens to bury him in cement. Archie falls for the blackmail and begs for his life, offering Phil money. However, the cement mixer only contains water. Phil tells Archie to leave, saying if he returns, he will be killed for real.
Archie soon returns on 10 July 2009, seeking to reclaim Peggy and reconcile with Roxy. He is revealed to have moved into a house near Walford, and refuses to leave the square at his family's insistance. Archie asks Roxy to pass on a gift to Ronnie: the baby blanket she bought for her daughter when she was born. Peggy eventually agrees to talk to Archie and believes he is sorry for his past actions. Phil sees him and breaks into his house with a gun, but sees him and Peggy kissing. Peggy tells Phil that Archie has changed, but Phil tells Archie to stay away from his family and drops a bullet into his glass. Phil later tells Archie he's going to kill him, but is stopped by Ben at the last moment. After returning from her holiday, Peggy refuses to recoup her broken marriage with Archie. Roxy invites everyone to Archie's housewarming party, but Ronnie organises a party at The Queen Vic - so nobody turns up. Janine tells Ronnie that Archie paid her to spy on her and Roxy, prompting Ronnie to tell her sister about this. In response, Roxy - furious with her father - moves out. Archie later buys the car lot from Jack, upsetting Ronnie further. Danielle's biological father, Joel, comes to Walford and he and Ronnie rekindle their relationship. This irritates Archie, who later bribes Joel to leave Walford and never return. Joel refuses, saying he can stand up to him now. Archie then resorts to blackmail by proclaiming knowledge of his family. Joel leaves in response, but later returns at Ronnie's request. She later tells her father that Joel is back and there is nothing he can do about it.
At somepoint, Archie discovers that Peggy's daughter Sam is back in Walford - having returned from Brazil despite being on the run for covering up the murder of the Queen Vic's original landlord and Phil's old enemy, Den Watts. He soon observes a feud between Sam and Roxy, as the pair have never got on properly; with Roxy growing frustrated to learn that Sam's return has been kept from her. Archie later sees Roxy in the Square, following a row, and she tells him. He also learns of Sam's engagement to Janine's brother Ricky and gives them a gift - which they decline. When Sam is arrested, Archie puts up her bail money on the condition he can have his family back. He and Peggy celebrate, but their children return the money and their cousin Billy makes it clear to Archie that his family - including Peggy - still don't trust him. Outraged, Archie vows to get revenge on his family by taking The Queen Vic from them. He forms a partnership with Janine to carry out his scheme. He first plans to burn the pub down and frame Billy for the incident, but Peggy discovers this - though Archie is able to convince her that he wasn't involved and they kiss briefly. Archie later causes his family to lose the bail money for Sam by convincing her to abscond the country. This prompts Phil to borrow money from a loan shark named Isaacs, who later assaults him for not meeting the repayments; in response, Phil gets a loan from his stepson Ian Beale - which is secured on The Queen Vic, thereby meaning that Ian would inherit the pub if Phil does not repay him in two weeks. Archie uses this opportunity to try and secure the Queen Vic by convincing Ian to sell the pub to him, but Ian refuses. Janine carries out Archie's scheme by seducing Ian, and record them having sex together. She then blackmails him into selling the pub to Archie, whom she claims to be in a relationship with; Ian is forced to agree when he fears the pair will expose the recording to his wife Jane and threaten Ben should the latter get involved. Archie later proposes to Janine for her efforts, and she accepts. Billy soon discovers Archie's plot upon hearing him and Janine talking about their engagement. After discovering that Billy had overheard their plans, they convince Billy to let them make him an offer so he could be on their side; Billy reluctantly agrees when they persuade his ex-wife Honey to let bring their children over for Christmas and New Year to spend time with their father.
When Archie and Peggy's divorce papers come through, Archie tells Peggy that he still loves her and wants her back. Peggy's employee and Janine's flatmate Ryan Malloy soon overhears them, prompting him to inform Janine about. Janine then shows her engagement ring to Peggy, who recognizes it as the same ring that belonged to Archie's mother. Upon realizing that she had been manipulated again, Peggy confronts Archie and signs the divorce papers and the Mitchells celebrate in the pub. However, their celebrations are cut short when Ryan alerts them to the fact that Archie and Janine are behind the bar. Their scheme is soon unraveled when Archie tells his family that the deadline has been overdue, and that Ian has already sold them the loan that basically grants Archie ownership of the pub. The Mitchells are outraged, but try to carry on as normal - prompting Archie to replace Peggy's name as licensee with his own; Archie then makes his ownership of the Queen Vic clear by telling his family that they are trespassing on his property. Ronnie later confronts and stands up to her father, which provokes Archie into slamming her into the bar. Roxy angrily tells him that Ronnie is pregnant, but the damage is done and Ronnie later miscarries. Peggy tells Archie that he killed another of Ronnie's child and warns him to stay away from her, but later invites him and Janine to The Queen Vic during a Christmas Eve party and gives them the keys; Archie and Janine celebrate as his family move out of the pub in defeat, though not before Phil warns Archie that he'll be coming for him.
On Christmas Day 2009, Archie sadistically tells Ian he will give the CD to Jane - despite Ian's compliance. Archie later convinces Janine to skip Christmas dinner as he has a surprise treasure hunt for her. She eventually finds an envelope containing a one-way ticket to Poland, and discovers that Archie has packed a bag for her to move out of the Queen Vic. Archie tells Janine that he is aware that she had been planning to defraud him in a conspiracy plan with Ryan, before taunting her with the fact that she is the reason why her father Frank abandoned her. After throwing Janine out of the pub, leaving her upset and seething, Archie is visited by a number of people whom he has antagonized throughout the year: Jack threatens to kill him if he hurts Ronnie again, he finds Ian searching for the CD and tells him that it is on his laptop and he can make copies at any time, threatening to phone Jane, before evicting him from the pub. Sam tries to confront Archie but he shuts the door on her. Ronnie tells him that he will not make her care for him and she would not care if he died. Archie throws her out, reminding her that of the exact spot she pushed Danielle onto the night she died. Peggy threatens him, telling him that she is not just a sweet, innocent old lady and that he has no idea who he is messing with. She tells Archie if he does not leave the pub that night he will regret every cruel and evil act he has ever done. In return, he threatens her that unless she returns, he will have the pub converted to flats, becoming emotional when he says that he will be waiting for her as she leaves. Later on, Jack's nephew Bradley visits Archie and punches him - hurting his fist and loosening one of Archie's teeth. Bradley warns him to stay away from his girlfriend Stacey Slater, due to the fact that Archie had raped her and is responsible for her being sectioned a couple of months ago. Once Bradley has left the pub, Archie picks up the snowglobe from the floor and shakes it around. As he does this, Archie doesn't notice the bust of the Queen Vic being pushed from the bar and coming straight towards him. Archie is struck on the head by the falling bust, and is left fatally injured. Moments later, his daughters find him - with Roxy arriving in the pub to see Ronnie crouching down behind their dying father. Archie then dies of the head injury, but not before blurting out "Veronica, I'm sorry." His body is taken away the next day. Archie's will is read, revealing that he has left:
Billy – his "stool" and place at the end of the bar in The Queen Vic, as a place for him where he cannot be thrown out; Peggy – a silver framed photo of their wedding; Amy, and Ronnie's first surviving child, the sum of £100,000 each to be held in trust until their 21st birthdays. Ronnie is unhappy, seeing this as Archie controlling her from beyond the grave, but is not allowed to decline legally; Phil – his father's "real" boxing trophy, which they had a fight about earlier regarding Archie giving fake ones; Roxy – his antique fountain pen which she always wanted as a child, as well as the residue of his estate, including his mother's engagement ring, his house (27 Albert Square), car, The Queen Victoria (46 Albert Square), the car lot (6 Albert Square) and £3 million;
Ronnie – his signet ring (as well as a note regarding him expecting her to not take any substantial gifts from him); Janine – his Newton's cradle, "in the sure and certain knowledge that it will drive her absolutely nuts."
A pathologist's report shows that Archie had terminal cancer and only had weeks to live anyway. On 19 February 2010, the killer is revealed to be Stacey, however, after dying while trying to evade police capture, Bradley is assumed to be guilty of murder. Later that year, it emerges that Archie raped Ronnie when she was 13. In December 2010, everyone finds out that Stacey was the murderer, and she flees the country, leaving her mother, Jean Slater, devastated and she blames Archie for Stacey's departure. In 2014, Stacey returns to Walford briefly but tells the police that she killed Archie to clear Bradley's name. She is sentenced to five years in prison, but later appeals the sentence on her mother's urging; Stacey is soon released due to her bipolar disorder, and her ordeal with Archie is over at last.