Hardest roads to a title
Title runs ranked by the average Elo rating of the opponents actually beaten (ratings as of match time, walkovers excluded, minimum four wins). "Best win" is the strongest opponent defeated en route.
Methodology
Each title run is scored by the average pre-match Elo of the opponents actually beaten (minimum four wins; walkovers excluded). Elo is computed over the full chronological match history with K = 250/(n+5)^0.4. "Best win" is the highest-rated opponent defeated en route.