I'm not sure if it properly fits the theme of "awful concept," but I hate the stupid broken overpowered Warshaper. As a shapeshifter of some sort or another, I can learn quickly (5 levels) to contort my body to gain extended reach, incredible immunities, free ability score and damage boosts that stack with everything, ultra-fast healing... the best warrior class ever.

Frenzied Berzerker: interesting concept, devastating execution that makes it unplayable.

Forsaker: same as above, but even more unplayable. At least the FB can be worked into a very forgiving and cautious party. The Forsaker loses class abilities if he stops destroying party wealth.