MMA legend Fedor Emelianenko ... SUCKS ... and he SUCKS HARD ... this according to UFC president Dana White.

White and Fedor have been at each other's throats for months ... a feud which reportedly began after the legendary Russian fighter -- who many claim to be the greatest mixed martial artist who ever lived -- refused to sign a deal to fight in the UFC.



Fedor's manager reignited the war just last month ... when he compared White to a greedy "dog" who runs the UFC like a prison.

But White fired back last night on his way out of Mastro's in L.A. -- telling photogs, "Fedor sucks man ... you guys need to get with the facts, deal with it ... he sucks. Get over the Fedor thing."

Sounds like a fight that NEEDS to be settled in the Octagon.

UFC fighter Jason "Mayhem" Miller was arrested last week for assault ... TMZ has learned -- after the fighter allegedly put his sister into a headlock and refused to let her go.

Law enforcement tells TMZ, Miller and his sis were at some house party in North Carolina -- when his sister decided she wanted to take off.

According to law enforcement, Jason's sister claims he wouldn't let her leave -- and put her into a headlock.

We're told Jason's sister managed to escape and notified the Chatham County Sheriff -- who had Jason arrested later that evening for simple assault and false imprisonment.

Jason has since posted bail and been released. Several calls to both Jason and his sister were not returned.