Yu Darvish
The all-time leader in this statistic through 2020 is Yu Darvish (11.12). The only other pitchers who have averaged over 10 strikeouts were Chris Sale (11.08), Max Scherzer (10.63), Randy Johnson (10.61), Stephen Strasburg (10.60), Jacob deGrom (10.46), Kerry Wood (10.32), Gerrit Cole (10.15), and Pedro Martinez (10.04). The top three in 2020 were Shane Bieber (14.20), Jacob deGrom (13.76), and Trevor Bauer (12.33).