I've been reading Marvel from Fantastic Four #1 forward across multiple titles and am now in 1981. One thing that's impressed me is how multiple writers/editors kept characters relatively consistent. Except when they didn't.
I mean some of that was Really Bad. Characters were simply written totally out-of-character every now and then, to a point that was offensive. Have you seen that?
My personal vote is X-Men King Sized Annual #5. The Invisible Woman had been steady growing as a character, and Claremont (who was usually a feminist writer) regressed her to an "helpless female" stereotype in one quick stroke.
So what's your WT* misrepresentation?