To throw my two cents about the Abomination (since the topic is about him after all), I actually find him stupidly hard at times. Not overly so, he's actually more annoying that truly challenging, but it can really become dangerous to drag the fight for too long.
THE AMOUNT OF MINES HE CAN LAY , HOLY ****.
Not to mention the legions of gooey zeds he can spawn. The Abomination is certainly the best example of a boss that seeks to overwhelm you... Which in itself is not half-bad. But the fact that he's very tanky, also forces you to run and funnels you with his mines... It can get infuriating quickly.
I guess I'm rambling more than anything, but my point is basically that I don't find the Abomination AS BAD as most players, nor as easy to defeat. But he's definitely cheap.