I have made the list keeping in mind entire careers and not just a stretch of dominance alone. Prime is subjective and we can't simply consider prime alone. 1) Khabib - Self explanatory, 29-0, never lost a fight, never dropped, never bled. The minor moments of vulnerability were a punch by MJ that startled him, a submission attempt by Poirier and 2 close rounds lost in entire career. One close fight with Tibau but nothing much happened in that fight, even though he won it 30-27 but it was at the very least not a dominating performance. 2) Jones - Never lost a fight discounting the DQ loss that he destroyed his opponent in. He had three close fights in Gus, Reyes and Santos and there were some competitive fights with DC. There were moments in Machida, Glover fights but he still dominated. All in all, he took more damage in each of his close fights than say Khabib's entire career but he should be far ahead of everybody else imo. 3) GSP - Dominated most of his fights and mostly won 50-45 completely neutralizing his opponents. Two losses where he got finished but avenged both losses in spectacular fashion. Also had a close fight with Hendericks and got dropped by Condit. Had a competitive fight against Bisping whom he finished. 4) Fedor - Dominated for a decade. There were moments where he looked very vulnerable like Fujita punch and Randleman slam. Had some competitve fights as well throughout his career but his aura of invincibility was second to none and people knew he'd find a way to win no matter what happens. Anybody picking against Fedor used to become a laughing stock. Eventually he lost brutally many a times especially that Bigfoot loss was terrible to watch. 5) Silva, like Fedor his reign of terror was a thing to behold. Absolutely destroyed his opponents while playing with them. He had some early losses though and in the middle of his reign he got dominated by Sonnen but still came out with a win. Eventually he lost brutally many a times like Fedor especially getting his leg broken multiple times. He now has a long list of losses. 6) Aldo - Aldo had a fantastic reign and only had one early loss. He had some competitive fights like Mendes 2, Frankie 1, KZ and even Hominick to some extent but mostly dominated. He eventually lost brutally with a 13 secs KO but reclaimed his belt and proceeded to get destroyed by Holloway twice where he put up a good fight. He is now on a 3 fight losing streak and has a bunch of losses. 7) Conor McGregor - Some might find this controvertial but Conor ran through all the FWs when he was coming up. He had a competitive fight with Mendes but still won by KO. Some of his wins like Aldo, Eddie, Cowboy, Poirier are the most dominant wins ever. He lost to Nate Diaz in embarassing fashion where he was actually beating Nate up initially and then won the rematch which he was again dominating in the start but it turned into a very close fight where Nate beat him up pretty bad. He then got absolutely embarassed by Khabib and beaten up pillar to post, however, he still managed to win a close round albiet he cheated quite a bit. His boxing loss doesn't count. He also had 2 pre ufc losses. 8) MM - Mighty mouse was extremely dominant throughout his reign and only had two early losses to Cruz and Pickett. He also had a very close fight with Mccall which was a draw. He mostly just dominated everybody after that for a long time and had a close loss to Cejudo. Honestly he could be a few steps up around 4-5 mark. For 9 and 10 I have many choices like Israel, Usman, Cejudo, DC, Romero who mostly lost close fights or fighters that had a great stretch of dominance but many losses eventually like Igor, Barao, Penn, Hughes.