Flaaayin poisoner with irresistible poisons, also got Quaggoth (publicly) nerfed while he was still playing
Hoysepis outlander svirf shapeshifter with gorilla form
-- this might be a tangent, but the guy who played these was one of the best non-IMM CFers, ever IMO. I briefly interacted with him while playing clash of clans a couple years ago, and it turned out that he played an incredible amount of memorable, game changing type characters that frustrated the hell out of me. And never publicly claimed any of them. I'm not sure if abilities got nerfed so much as he is better than 99% of CFers at figuring out how to play the game.
I never heard of the other characters on your first list so can't comment on those except for Forodaugh who, despite making the most use out of bat ever, really didn't impact the game or cabal dynamics much and deleted at about the time he could have .. kind of a typical Nep approach to under the radar domination in that regard.
On the second list, I don't remember/doubt Kostyan getting STSF nerfed, but lashes definitely did get tweaked after Ravon. While Ravon was still playing, right? I suspect the reason why that was more of a "public" nerf was because of the difference in how different players reacted when the nerfs happened.