There's no such thing, even King Kong wasn't invincible, and neither is any man.

The secret of the so called 'Good Chin' is making yourself harder to hit, limiting your opponent's options so you know what's coming, and knowing how to take a punch (moving into it, away from it or like the phrase goes, 'rolling with the punches'). Conditioning and a champion's tenacity plays a big part as well.

Guys like Marciano, LaMotta, Chavez, you name it did a lot of these things and there performances speak for themselves. These guys were so well trained and conditioned that they knew what to do when they're hurt, they were able to fight hurt, or dazed, they knew how to clinch or survive if need be.

A good stance and biomechanics/alignment that doesn't hinder you in any way, and good equipment is important as well.