Kramnik ((ab)using his status as a former world champion) accused several other top level players to the point that one of them committed suicide.
Niemann allegedly cheated (In my personal opinion as a decently rated but certainly not elite chess player, he probably did cheat in this particular game, though proof was never given and probably never will) at a high level chess tournament and was ostracized by the chess community for a while. He has since rejoined and continues to play at a high level.
Kramnik ((ab)using his status as a former world champion) accused several other top level players to the point that one of them committed suicide.
Niemann allegedly cheated (In my personal opinion as a decently rated but certainly not elite chess player, he probably did cheat in this particular game, though proof was never given and probably never will) at a high level chess tournament and was ostracized by the chess community for a while. He has since rejoined and continues to play at a high level.