Caesar's (Andy Serkis) ingratitude is perhaps more down to Dr Will Rodman's (James Franco) awful parenting than any predisposed chimp rudeness. Still, few characters on this list play a major part in the fall of humanity just by having a bit of a sulk. Caesar has his fair share of bad luck and run-ins with the worst that mankind has to offer. Rodman's next-door neighbour injures him, his uber-intelligent mother, 'Bright-Eyes,' was killed by a security guard, and when he beats up the aforementioned neighbour he is imprisoned in a primate 'sanctuary' run by Brian Cox and Draco Malfoy enough to turn anyone against homo sapiens. The brainy chimp turns ungrateful chump when he refuses to go 'home' with Rodman once he comes to pick Caesar up from the sanctuary, conveniently forgetting that Rodman is responsible for bestowing on him his heightened intelligence and ability to speak. He also dressed him up like a student on his gap year, but that's probably more of a 'con' than a 'pro'. It's also clearly evident from Rodman's expression/James Franco's emoting that he genuinely loves Caesar as a son. Instead of accepting that, just like apes and chimps, humans can be both bad and good and life sometimes lets you down, Caesar decides to fight back against humanity. This act of defiance coupled with the new strain of Rodman's Alzheimer's cure will eventually bring about the end of the world as we know it. Ungr-ape-ful.
