First 2 to come to mind:
Dragonman. I remember, first time seeing it, I thought, What? Just take any word and stick 'man' onto it? It's grown a bit on me since, but it still strikes me as somewhat ... plebian.
The Thing. Really? Were Lee's and Kirby's imagination on hiatus that day? I mean, ok, back then it kinda worked. But there have been so many more, and more monstrous characters intro'd since then, that 'the Thing' seems misplaced or used prematurely.