Nate Diaz. He beat Conor but has won fights at a higher weight class than he started his career in. Diaz has beaten much larger opponents than CM like Cerrone, Maynard, Marcus Davis(WW), and 177 lbs Markham by TKO.
Conor only has success against 5 8 and under guys with less reach who could probably compete at 135-145. He loses at 155 and gets murdered at WW.
Fact Nate won TUF at lw and has done 90% of his fights at LW. He is not a natural ww. He probably walks around 175 to Conor's 170. Not that far off size wise just Lankier.