On the biggest night in recent UFC history, Justin Gaethje forced Ilia Topuria to retire at the end of Round 4 of their UFC lightweight championship fight to become the UFC undisputed lightweight champion of world. Gaethje, a major underdog heading into the fight, beat up and battered the previous undefeated Topuria all night so bad he had grotesque swelling in both eyes and was bleeding profusely all over his face before his corner stopped the fight.