The answer to this is impossible to say.
I’m a massive Andy Murray fan and he won quite a lot in what some would say was the greatest era of the sport
I’m a little surprised Seb Coe didn’t make the list.
Off the top of my head.
2 x 1500m golds
2 x 800m silver
Broke every world record 800, 1000, 1500 and mile and possibly held them all at the same time. Broke all of them in a few weeks if I remember correctly
But for me his greatest achievement was holding the 800m world record for over 20 years. Maybe even have been a quarter of a century. I doubt even now many people have run as fast as he has for 800m
After a quick lookup his WR lasted 16 years but his still joint 3rd fastest in history