Probably none. He's never been in a war with a big puncher because he has the skills to not. The 3 notable punchers he's been in with were Stevens, Jacobs and Lemiuex. He boxed all of them and didn't take much punishment from any of them. Stevens did hit him a little bit, but that was when GGG was younger and in his prime. And fought in his classic pressure style lending himself to take more shots. Take one to give one as they say. But even when Stevens landed all GGG was back up and take a momentary breather and continue on. He was never wobbled.
None. Maybe Canelo and Jacobs since they are the two that hit it most often and with good pop. You don't need a great chin to stand up to shots from Murray, Geale, Wade, Rosado, etc.
It GGG had been cursed with an Amir Khan level of Chin we know he would have been KTFO by both Canelo and Brook. But his iron clad mandible is part of his armour so it’s not even a consideration. It’s Oliver McCall proof.
The Kazakh government has a picture of Golovkin’s chin on their paper currency, that should tell you how great and sturdy Triple G’s mandible is.
His chin is his most valuable asset. If he fought better competition over the span of his career, it would’ve already been cracked. He’s barely faced power punchers.
He would have fought quite differently if he didn't have a chin, it's hard to say. With a Khan-grade chin I'd guess Canelo would have beaten him. Jacobs might have but he didn't land anything really big in my recollection, so not sure. Can't rule out an earlier upset with that sort of glass, but I wouldn't pick any.
... he's doomed, LOL. Only somebody as freaky-fast as Khan could have success with his toilet paper chin.
Haha perhaps. However I do wonder if a major factor is that Khan leaves his chin out in the air while Golovkin tucks his in very well. I suspect if Golovkin tucked in his Khan-chin he'd be able to take more than most of us suspect.
There's quite a few guys that have never had their chins cracked even after staying around longer than they should've. As for the original question: Golovkin's chin is a fail safe, the few times it's been tested, it passed. Of course, he's an above average boxer so thankfully for him he doesn't need to rely on it.