Most hateful TV character in prime time

[Michael Daniels]

As in, a character who is nasty, ill-mannered and has no redeeming attribute whatsoever.

Live action:

The whole cast of Will and Grace (sorry, but I loathe every character in that program. They make the Seinfeld characters look positively saint-like in comparison). And speaking of Seinfeld...

George Costanza (Seinfeld) Even competing against the other self-absorbed characters in the program, George takes it due to his not so repressed rage at everything and everyone

Major Frank Burns (MASH) - No justification needed.

Animated:

Tie between Khan and Cotton Hill - (King of the Hill) Two racist, bitter men who have utter contempt for their own families.