The cat in question is near ten years old. His story is a tragic one. As a kitten, he and the rest of his litter were occupying a window well when a torrential downpour started. As a shining example of Darwinism at work, Aggro Kitty (name changed for identity protection) was able to stay afloat while rain water quickly filled the well. The rest of the litter never made it. 

AK was then saved by its current owner's mother, who couldn't simply leave AK to fend for himself after loosing his entire family. The kindly mother passed AK on to her son-- then in his early twenties. The son provided AK with shelter, food, and an apartment on the fourth floor; far, far away from any window wells. A year later, AK was given a friend to play with (we'll call her Ditzy Kitty, but she's another story) and keep him company during the long days his owner spent away at work or whatever.

Considering the great life that Aggro Kitty's owner has provided, one would assume that AK wouldn't be all that aggravated. With all the horrors of being an outdoor cat behind him, AK seemingly has nothing to worry about other than which couch or chair he's going to spend the next three hours on. In his old age, one would think that AK would be content lounging, perhaps even getting a little fat while totally spacing out on catnip. Maybe he would be the type of old, mellow cat that rolls around on the floor like a weirdo and purrs super loud when you pet him.

None of that's true. Aggro Kitty is the angriest cat alive. He loves hip hop, mind games, and punching the shit out of any human legs that enter his bubble. And he's certainly not afraid to bite a mother fucker.