I wish baseball-reference.com had versions of OPS+ for other batting stats, i.e., factoring year and parks: BA+, SLG+, ...
A few years ago for seasons, not career, I figured percent above league average for slugging average (SLG) and batting average (BA).
In only three seasons was it above 100%, i.e., more than double the league average:
Ruth 1920 119.3%
Ruth 1921 107.3%
Bonds 2001 103%
This is followed by Ruth, Bonds, Ruth, Bonds, Gehrig, Williams, Williams, Ruth, Ruth, Foxx. Ty Cobb 1909 DET 67.28% was number 100.
One batter slugged more than 50% below the league. Here are the three worst:
Bill Bergen 1909 BRO -50.25%
Wayne Tolleson 1987 NYA -43.43%
Dal Maxvill 1970 SLN -43.09%
There were only 12 seaons in which batters were more than 50% above the league. Only 2 of those 12 were after 1917, both by Ted Williams: 1957 52.25%, 1941 52.24%. They are ranked 10 & 11. Ty Cobb takes 7 of the top 12.
Best: Nap Lajoie 1910 CLE 58%.
Worst: Bill Bergen 1909 BRO -43.1% Bergen was also worst in SLG.
Why is the top slugger more than twice as much above the league as the top BA: 119 to 58?