In soccer, I despise Man-U. It's all about ARSENAL, bitches!
The basketball team I hate the most is the Indiana Pacers. The New Jersey Nets come a close second.
In football, the teams I used to despise the most were the Indianapolis Colts and the Pittsburgh Steelers, but now it's back to my division rival New York Jets and Miami Dolphins.
The baseball team I hate the most (and my most hated professional sports team of ALL time) is, of course, the New York Yankees. I've actually dreamt about murdering Karim Garcia back in 2003 (when he was a Yankee), but that Red Sox World Series win did a lot to slake my bloodthirst.
I still hate them with a passion... but that Mariano Rivera's A-OK in my book.