As a Magnus Carlsen fan, it was a bit disappointing for me to see him finish clear second in Biel 2018, one and half points after Mamedyarov, after starting the tournament with two wins - and it could have been two points - had not the much lower-rated Georgiadis blundered in a drawn endgame. Although not a bad performance per se, I was wondering what were the worst tournament performances of reigning World Champions?