Basically,which person or incident did the most harm or was the most embarrassing for the sport? I would say PEDs .. But the cocaine thing wasnt good either......
Personally the 1994 strike. We were season ticket holders and haven’t been to a game since. I was always a Tony Gwynn fan and he was flirting with batting 400 that year.
Black Sox scandal remains the gold standard for black marks in MLB history, IMO. PEDs are a distant second. I pick these two because each provably impacted the outcome of games. To that end, the Astros sign-stealing scandal of 2017 via electronic means was also a big one.