Answer
Spassky's peak Elo rating was 2690, which he achieved in July 1972. This was the highest Elo rating ever recorded at the time, and it remains the second-highest Elo rating ever recorded, behind Magnus Carlsen's 2882 rating. Spassky's peak rating came during his victory over Bobby Fischer in the 1972 World Chess Championship, which was one of the most famous chess matches in history.