How durable is MCU Captain America

In spite of the brutal punishment Cap's shield has been able to take over the years, it's still been destroyed ... and more than once. The bulk of these destructions have taken place in alternate universes, or they have otherwise been reversed. 

One of the first to break Cap's shield was the supervillain Doctor Doom. In the iconic 1980s storyline Secret Wars, Doom acquired the powers of the Beyonder, one of the most powerful beings in the universe. With this new power, Doom was able to obliterate Cap and his shield, but the Beyonder soon brought Cap and his shield back to life. 

The uber-powerful villain Molecule Man, who has the ability to manipulate the molecules of anything, also destroyed Cap's shield. Not only that, but in a tremendous show of power, he did it while simultaneously disintegrating Thor's hammer, Silver Surfer's surfboard, and Iron Man's suit. He later used his powers to reassemble all of the items. 

Thanos holds the distinction of being the only one to destroy the shield in both the comics and the MCU. In the Infinity Gauntlet comic book storyline, Thanos shattered the shield with one punch while in possession of the gauntlet. In the MCU, he hacked chunks of it off with his enormous blade, and he didn't even need any Infinity Stones to do it! When it comes to wrecking Cap's shield, Thanos is clearly the king.