C_chess_T #1The Greatest Chess Blunder! Kasparov has put stalemate instead of the checkmate! youtu.be/581pf-IVguk
michalpiotrowski #2i think 21. ... Qxf1 in pl.lichess.org/fXTTBVY2#41 is bigger mistake. It was in his last classical game ever. He was sure 1st place in this tournament but he lost to runner up. After other move order it should be easy draw.