Gary Morris
Artur Sowinski
Dave Hill
Max Holloway
Dennis Siver
Chad Mendes
Nate Diaz
Nate Diaz
Eddie Alvarez
Floyd Mayweather
Khabib Nurmagomedov
He's only decisively lost 5 rounds in his entire career. 1 to Diaz, 3 to Mayweather, and 1 to Khabib. But he won the majority of rounds against all three of them.
And obviously it needs to be said that he doesn't have as many completed rounds as most, because he knocks most people out in the first round:
Ciaran Campbell
Mo Taylor
Stephen Bailey
Connor Dillon
Hugh Brady
Mike Wood
Paddy Doherty
Aaron Jahnsen
Steve O'Keefe
Ivan Buchinger
Marcus Brimage
Diego Brandao
Dustin Poirier
Jose Aldo
Donald Cerrone
Do you think we'll ever see a better fighter than Conor McGregor in MMA?