Andrei Arlovski. People here make it sound like he dies the instant he gets touched. In reality his striking defense is almost non-existent and he takes nuclear bombs right on the chin all the time. His reactions to getting hit are usually the problem. Freezing up or backing up with his chin straight up in the air. He withstood Rumble's onslaught after a broken jaw in the first and also got cracked with a massive counter punch from Browne and survived in both of those fights.
Another one is Frank Mir. His problem is really similar to Arlovski's, bad reaction to getting hit or just flat out non-existent defense. He withstood Overeem's onslaught, and took massive punishment from JDS and didn't go down for a while. Carwin is regarded as one of the heaviest hitters in HW history if not the hardest hitter and it took like 3 dozen strikes to put Mir completely out, AND it was a retardedly late stoppage. Outside of the Mark Hunt fight and Barnett fight (early stoppage tbh), everytime Mir has gone down it's been from a barrage of strikes.
Not saying Mir or AA have "good" chins, but they aren't glass like people suggest IMO
Ben Rothwell's chin is known as being good already, but I have it pegged as one of the best of all time. Took a murderous overhand right from JDS and didn't budge, non-chalantly stalked the fuck out of Overeem and ate all of his strikes like they were nothing, walked into an overhand right from Mark Hunt who then tried to walk away not realizing the fight was not over, and was trying to stand up in the midst of Cain hitting him in the face. Pretty ridiculous.
