At age 33, Fedor was 31-1 (1), beating multiple future and former champions and ruling the HW division of MMA for 6.5 years with a Mike Tyson like mystique.
Also, if not for weird Japanese rules back then, he would not have that "loss". Basically the ref stopped the fight 17 seconds in the 1st round after a cut opened above Fedor's eye from an illegal elbow and awarded his opponent Kohsaka got the win. Japan had a weird thing that they didn't want any blood shown and no fight would have gotten stopped for that anywhere else in the world. Later in PRIDE Fedor whooped Kohsaka anyway.
The no-contest was against Nogueira, after an accidental headbutt in the 1st round. He beat Nog twice decisively.
Not counting the abnormalities, he is 31-0 against better competition.
It's safe to say Fedor is the greatest Russian MMA fighter (as well as the GOAT HW).