5. "The Notorious" Conor McGregor
A slightly controversial choice at number 5 but I have chosen Conor McGregor. Despite having only a 1-1 record at lightweight, including his historical victory over Eddie Alvarez at UFC 205 in 2016 and his submission loss against Khabib Nurmagomedov at UFC 229. He was also very inactive as a lightweight champion as he didn't defend his belt at all. However, he still did dethrone one of the greatest lightweights in all of MMA and has defeated top lightweight contenders Dustin Poirier and Donald Cerrone at featherweight and welterweight respectively.
4. Frankie "The Answer" Edgar
At number 4 is the former UFC lightweight champion, Frankie Edgar. Although Frankie has not fought in the lightweight division for a long time now he had successfully defended the lightweight belt 3 times including a second victory over Bj Penn, a draw, and a win against Gray Maynard. He ended up losing the lightweight title to Benson Henderson by unanimous decision and then losing a rematch to Benson by split decision. After this Frankie decided to drop down to featherweight and despite having many chances to win the title he was unsuccessful and has since dropped down to bantamweight where he is currently 1-0 after defeating Pedro Munhoz by split decision.
3. Benson "Smooth" Henderson
At number 3 is current Bellator lightweight contender Benson Henderson. When he joined the UFC he went on a three-fight win streak which included wins over Clay Guida and Jim Miller. This resulted in him receiving his first UFC title shot. He defeated Frankie Edgar by unanimous decision to win the belt and in the rematch got a split decision win over Edgar in their rematch to defend the bel for the first time. He defended the belt twice more against Nate Diaz and Gilbert Melendez before losing it to Anthony Pettis in 2013. A fight in which he tapped out to an armbar with 19 seconds left in the first round.
2. "The Prodigy" Bj Penn
Coming in just short of first place is Bj Penn. He was a former two-weight division champion in the UFC as he had won the welterweight belt before leaving the UFC and once he returned he defeated Joe Stevenson for the lightweight title. He defended the lightweight belt 3 times against Sean Sherk, Kenny Florian, and Diego Sanchez. Bj Penn was a fantastic BJJ fighter and despite this, he was able to get a few KO/TKO wins and was one of few fighters to be able to win two titles in the UFC at that time.
1. Khabib "The Eagle" Nurmagomedov
At number one without question is Khabib Nurmagomedov. Khabib has dominated all 29 of his opponents inside the cage using his dominant wrestling to do so. Khabib defended the lightweight title 3 times against Conor McGregor, Dustin Poirier, and Justin Gaethje. He submitted all three of the guys named above. Khabib fought yesterday (at the time of writing) against Justin Gaethje and announced his retirement in an emotional post-fight interview.