UFC heavyweight champ Stipe Miocic SMASHED Francis Ngannou at UFC 220 -- but you wouldn't know it by looking at his mug the day after the fight. Stipe posted a thank-you video to his fans ... and the shiner he was rockin' after the scrap had grown into the size of a damn golf ball. Dude's left ear looks like it got mangled, too. Francis, meanwhile, barely had a scratch on him ... even though he got worked from bell to bell. Doubt Stipe cares, though -- dude's the UFC heavyweight G.O.A.T. now.