Rob

After his escape from the Void, he temporarily develops amnesia and becomes somewhat depressed. He lives in the basement of the Wattersons' house until Gumball and Darwin become suspicious of his stolen goods. They eventually track him down, and after cornering him, they force him to explain his actions. When they mention that there really isn't a villain in Elmore, the boys suggest he become their arch-nemesis - a suggestion that triggers his memory. He recounts how he begged the boys for help as they passed him in the Void, and how they ignored him and went for Molly (though they failed to notice him). His villainous backstory set, he swears vengeance on the boys for abandoning him and agrees to become their arch-nemesis.

As a villain, Rob has a very nihilistic philosophy on life. He becomes vengeful and bitter. No longer does he care about the well beings of others, and only cares about getting revenge on his self-sworn nemesis: Gumball. This is evident in "The Bus" when he kidnaps both the students and the adults aboard the bus with plans to blow them up simply because he hates Gumball. Such a philosophy is explored even further in "The Disaster" and "The Rerun," in which he becomes aware of his fictional status and wants to make Gumball's life as miserable and broken as possible for the way he's treated on the show.

Despite this, "The Rerun" does show he has a heart as after Gumball attempts to save him, he sacrifices his friendship with Gumball to return to his villainous lifestyle and undo all of the damage. This attitude changes, however, in "The Ex," when Gumball foils all of his plans to destroy Banana Joe, and at the end of the episode, re-establishes his hatred for Gumball. However, in "The Inquisition," he tried to save everyone he could from a mysterious threat by turning them into humans showing that he does value the lives of others though unfortunately he failed due to everyone either not listening or believing him.