You always have to look at the board
The homepage for chess.com tournaments includes the event's biggest upset. In a Sicilian theme tournament, the biggest upset has been a 1300-rated opponent beating 1800-rated me.
It was a Main Line Najdorf where I remembered 12 or 14 mainline moves, until a bad move. One grandmaster showed another, which he copied until I resigned. In the rematch, we thought for ourselves. I had white and the move:
