While you do make a solid point, Mirko's younger and still has some fight left in him, plus if I'm not mistaken, Kick-boxing gloves are thicker, so your fist is more covered causing punches to be less effective and KO's to be harder to come by.
If you asked me, I'd probably say Chuck's chin is a lot more faded, being that his losses were more devasting. Maybe Mirko's last 3 MMA fights were KO losses, but he was still able to put up a fight for 3 rounds. With Chuck Liddell, you're talking about someone who couldn't even make it out of the first round in his last two fights. That would lead me to think that If he were to fight again, he probably wouldn't last half a round.
I wasn't comparing the two. Just that Mirko found a way to work with his faded chin by returning to his roots, Chuck doesn't have that option. But you're right, Chucks case is a lot worse than Mirkos.