Want some live ones?
I'll take the most recent 20 seasons' best OPS and throw out Bonds.
I should throw out Sosa and McGwire, too as both of them used PEDs and saw a massive spike in their OPS and then equaled or topped that spike later in their careers.
Here's the rest:
#6 Larry Walker: He has a three seasons over .900 and a .912 OPS in 1996 before exploding with a 1.172 OPS in 1997 (6th best in 20 years). He ends up going over 1.013 5 more times, including coming very close to his 1997 high twice: 1.168 in 1999 and 1.111 in 2001.
#7 Todd Heltom: His 2000 season was about 180 points better than his previous high (just like Mookie), and he came close the following year with a 1.116 OPS. He then had 3 more consecutive seasons over 1.006.
#8 Manny Ramirez: He jumped up to a 1.105 OPS in an insane 1999 season (44 HRs and 131 RBI while batting .333)! Can't top that, right? Well, the very next year, he has his 1.154 OPS season the year before signing with the Sox. He ends up having 6 more seasons over 1.009, including one pretty close to his 2000 season in 2002, when he hit 1.097, which even as his second best of his career was still better than Mookies' 2018 season.
#9 Jason Giambi, someone you know. A good example for my case. He jumps 100 points in 1999 with the A's to a .975 OPS. In 2000, he has a "career best year" of 1.123- a similar jump as Mookie of about 150 points. Except, it wasn't his career best. He did better the next year and by 124 POINTS! He hit 1.137 in 2001 the year before joining the Yanks and beginning his slow decline, despite a 1.034 first year with them.
#10 Carlos Delgado: I agree he was sort of a one and done player. His 2000 season's 1.134 was a bout 180 points higher than his previous season, but he did have one more season at 1.019.
#13 Jim Thome: in 1996, Thome jumped his OPS by about 70 points to 1.062. Pretty damn good. He followed it with a 1.001 OPS and 4 years later a 1.040 OPS. That 1996 season had to be his career best, right? After all, he was now past prime. WRONG! He went on to hit 1.222 in 2002 and even had a couple more seasons over 1.000 much later on.
#15 Luis Gonzalez: The true one and done. .952 in 1999, 1.117 in 2001 and never above .934 afterwards.
#17 Albert Pujols: He really had no spikes. He started off his career with amazing numbers right out of the gait. In 2003, he hit 1.106, which was almost 100 points better than his next highest. He then hit between .997 and 1.072 the next 4 years before topping his career best with a new one at 1.114 in 2008. He came close the next year at 1.101 (3rd best of career), then 1.011, .906 and then fell off a cliff with the Angels.
Those are all the top 20 OPS seasons in the last 20 years not named Bonds, McGwire or Sosa. These guys are still alive.