22. Georges St-Pierre
St-Pierre is arguably the greatest UFC fighter in history. He remains the most successful welterweight in history. After a contentious victory over Johnny Hendricks in 2013, he took a hiatus from the sport (via MMA Fighting).
After four years he returned and defeated Michael Bisping to become a two-weight champion. But then he immediately vacated the title to leave the UFC hanging. This catapulted the middleweight division into a mess and it took another two years to stabilize.