Oh yeah, definitely! Iron Man first had a turn in the 90s. He was mind-controlled and all, but still, there were a lot of deaths. His teenage self was brought in to fix the mess, but really, I feel like it was a way for the writers to rejuvenate the character and start young. After a few months, the two were merged and the bad deeds were forgotten. 90s comics were weird. He had a second turn not too long ago when he was struck with an "inversion" spell that turned the good guys bad and the bad guys good. That time, he was more just a cockier version of himself. He wasn't really "evil", he just didn't care about others as much.

Captain America turning evil was a big issue a year or so ago. A lot of people were up in arms about the whole thing, with many boycotting Marvel. The internet was on fire for months haha! What happened was that a sentient cosmic cube "rewrote" history to give the Nazis the World War II victory. Plot twist: it turns out they really were the winners, and the allies winning is the real tampering of history. Yadda yadda yadda nazi regime, heroes revolt, and the cosmic cube "reboots" the original Captain America. Now, there are two Steve Rogers-es running around. The good one, and the Hydra Supreme Leader.

In the end, that's all that really matters I guess. What's the use of stories if they're not enjoyable, right? It's tough to please everybody, so as long as good stories are being published, that's all that's important.