Obsidian will smash and hopefully end the fight before all his gargantuan muscle mass demands more oxygen than his CV can deliver. Assuming he has good cardio, im predicting he can last about 40 seconds of sustained ground and pound. A well placed knockout blow and its over. If tiny tit gets him to the ground, it might be the end but also might not depending on how accurate the inevitable.crushing blows from Obsidians elbows are.
I would lean toward Obsidian as a 3to2 favorite. Not a comfortable, easy win but a loss would genuinely be an upset so says I.