Earlier this year, Bill Perkins and Landon Tice played a very special heads-up match where Tice spotted Perkins 9 big blinds per 100 hands played (which equated to Perkins winning $720,000 at the start of the match).
When I made this video, the pair had completed just over 10% of the match, and at that point, Tice was winning at 10bb per 100 hands. To put things in perspective, a very good heads-up play against a bad heads-up player could be winning as much as 20-25bb per 100 hands. Tice has since conceded the match.