Rob

Rob is the main villain of The Amazing World Of Gumball.

Originally a mistake in Elmore that was sent to the Void, Rob broke out and, not only becoming disfigured, became an evil, dark, manipulative villain who, after adopting the mantle "Dr. Wrecker", wants nothing but to cause chaos in Elmore, eventually becoming Elmore's biggest villain and the archenemy of.

Personality
Rob was formerly a friendly, sociable person who would say hi to anyone, and would help people he knows if he happened upon them. He does, however, get deeply offended when someone forgets his name. When one of his friends forgets his name, he scolds them, and will even hinder their progress if he can. Two examples of such friends are Gumball and Darwin, who mistakenly call him several different names in "The Pony." After his escape from the Void, he loses his memory for a while 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 and agrees to become their arch-nemesis.

As a villain, Rob has a very nihilistic philosophy on life. 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 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.

Trivia

 * In general, Rob is a minor character in season 1 and 2, a major antagonist in season 3 and 5 and the main antagonist of season 4 and presumably season 6.
 * He is voiced by Hugo Harold-Harrison, and his Dr. Wrecker voice is voiced by David Warner who voiced Ra's al Ghul in Batman: The Animated Series.