Seymour Skinner (seasons 9-30)

Seymour Skinner is a major character and an antagonist from the long-running American animated sitcom The Simpsons. He is Bart Simpson's principal, and arch-nemesis. Sadly, he was flanderized.

Why He Sucks Now

 * 1) Unlike most other The Simpsons characters who were flanderized, Skinner was flanderized very quickly. Early appearances had him mainly as a reasonably competent, no-nonsense principal who was a Vietnam veteran and had an overbearing mother.
 * 2) He even managed to be pretty badass in a few episodes ("The Boy Who Knew Too Much").
 * 3) After a few seasons, he became a pathological mama's boy who was still a virgin in his 40s and merely embarrassed himself whenever he tried to assert authority over Bart or any other students.
 * 4) He even became an unfunny jerk within the process.
 * 5) He provoked Bart into pranking more by pranking him in front of the whole school.