These two heroes are the best friends of Alex, and they are probably the worst people you have ever seen. They all raped and killed a wife of F.Alexander. So, what can be worse? Probably the author of the text decided to make characters which will be the worst representatives of the society in order to show how they will change or not.
Also, Dim and George are initially members of Alex's gang. Dim is your stereotypical strong-but-dumb thug (dude's name is "Dim," after all) but he has a problem with Alex's authority. Dim is the biggest, dumbest, and most brutish of the four Droogs, and Alex describes him as a “mindless, grinning bulldog.” Dim is always saying bad worst and doing everything he wants too. Moreover, sometimes he doesn’t get to the end jokes people are saying; he can even accept them as an insult.
By the way, Georgie is smarter and more ambitious—he leads the rebellion against Alex for the sake of financial gain. Another member of Alex’s gang of hoodlums. Georgie tries to usurp Alex’s power within the gang at the beginning of the story. He becomes a thuggish policeman and dies in a later raid. Well, no one will cry because of it. Such people can’t live for long. Okay, let’s talk without prejudices.
Both are traitors to Alex: Dim incapacitates Alex at the Manse site, leading to his arrest, and ultimately becomes a police officer, lots of thanks to the program introduced by the Minister of the Interior. In this position, he gets even with Alex.
Though the stupidest member of Alex's gang, Dim is perhaps the most important. Alex's hitting Dim incites the group's eventual betrayal of their leader, and a great irony occurs when Dim shows up in Part Three as a member of the new, brutal police force.