During Captain America's one-on-one fight with Thanos (Josh Brolin) during the movie's climactic battle, the villain repeatedly hacked it with his sword resulting in the iconic shield getting fragmented.
Although vibranium is susceptible to damage, it's depicted as the most durable material in the Marvel Cinematic Universe. The fact that Thanos possesses enough power to beak vibranium is a testament to the strength of the Mad Titan, but more importantly, the weapon itself.
At the end of the issue, Tony Stark uses some of the magical metal, Uru, which was used to make Mjolnir, to also fix Captain America's shield, but now with a scar from the effects of the breakage. Tony offers to buff it out, but Cap says to keep it, as he thinks it gives the shield character...
After the battle, the shield is repaired by Asgardian dwarves and Tony Stark with added Asgardian uru-infused enhancements and Stark's own technology to make it stronger, though a scar is left, which the dwarves are unable to remove.
How did Captain America get his shield back in Endgame?
Captain America proceeded to ambush the soldiers, but as he attempted to use his shield to break one soldier out of a Parasit, another knocked the shield out of his hand. Once Captain America had flown the final Parasit back on board the Valkyrie, he reclaimed his shield.
5 Reasons Thanos Managed To Break Captain America's Shield
Why was Captain America old at the end of Endgame?
Due to what Thanos did and the discovery of time-travel by the Avengers, the world of MCU branched itself into many other realities. So Cap travelled back to another reality in which he did not spend 66 years unconscious and frozen in ice until he was discovered found by S.H.I.E.L.D. in 21st century.
In Marvel Comics, adamantium and vibranium weapons have gone toe-to-toe on several occasions, and the former usually comes out on top. However, in Marvel's live-action projects in the MCU and Fox's X-Men Universe, vibranium is clearly the stronger substance, and the more versatile.
More crucially, he says that his father King T'Chanda had gifted Howard Stark some Vibranium to help the war effort in the 1940s. In other words, Captain America's shield was made from Vibranium the secretive African nation freely gave to the Americans. Howard Stark: Your Highness, it's a pleasure.
At the end of Captain America: Civil War, Tony Stark tells Steve Rogers that he doesn't deserve his shield, since he kept his knowledge of the Winter Soldier killing Tony's parents from him. After that, he decides to ditch the shield and leave it (and a lot of things) behind him.
The ultimate reason that Sam handed the shield to the Smithsonian was that he didn't believe he was worthy of it. Steve Rogers did, though. Sam not believing in his ability to carry the shield was the worst betrayal of the Star Spangled Avenger's legacy.
Mjolnir doesn't damage Cap's shield at all, as shown below. I think it is fairly safe to assume that Stormbreaker (being a cutting weapon, rather than Mjolnir which is designed to smash or build) would inflict similar damage to the shield as Thanos sword does. Conclusion: Stormbreaker minces Cap's shield.
After Steve Rogers retired to a parallel timeline where he grew old, he returned to the main timeline with a new intact shield that he passed on to Sam Wilson. Feeling unfit to take on Steve's mantle, Sam turned it back to the government, who appointed John Walker as the new Captain America and gave him the shield.
Storytelling-wise, however, limiting her presence in Avengers: Endgame made sense, considering that it was meant to be the original Avengers' final outing. Marvel Studios found a way to explain her absence for the majority of the film, with Carol saying that she was busy helping other planets recover from Thanos' snap.
Many viewers have pointed out that Thanos was able to lift Stormbreaker without a problem, but this is because the ax isn't enchanted as Mjolnir is. Others believe Thanos lifted Mjolnir (although briefly) and have even argued that he would be worthy of doing so.
Thanos and Hulk have clashed several times in Marvel lore, with Thanos even admitting he was scared to face the Hulk before acquiring the Infinity Stones. While Thanos is usually the victor, it's generally down to him using superior tactics and technology, rather than simply possessing greater physical strength.
While it has never been confirmed what Thanos' sword was made of, the Endgame battle hints that it was made of Uru or at least some metal that was as strong as the one from Nidavellir. Thanos was facing, at the same time, Mjolnir, Stormbreaker, Captain American's Vibranium Shield, and Stark's nanotech.
Throughout Marvel Comics, the Hulk has tried and failed to break Captain America's shield but has never even come close, and since Superman is only a little bit stronger than the Hulk in his base form, it makes sense that Superman wouldn't be able to break the shield either.
Captain America's shield, while strong, has a weakness against supernatural forces like demon fire. The shield, made of vibranium, can absorb energy waves, but is not as effective against magic and demon attacks. Captain America must adapt his tactics to overcome this weakness and defeat Asmoday.
Summary. Dargonite, an alloy from the future, is stronger than both Adamantium and Vibranium in the Marvel Universe. There is evidence to suggest that Dargonite has already been introduced in the MCU, as seen in Avengers: Infinity War and Avengers: Endgame.
However, the majority of the more-advanced suits, starting with Mark III, were made not of iron but of a titanium or titanium-gold alloy. In the 2019 film Avengers: Endgame, the suit was constructed of vibranium and nanotech.
James Kakalios, a physics, and astronomy professor at the University of Minnesota suggests a substance known as graphene would be the closest substance to vibranium known to man. Graphene is an ultra-thin form of carbon; only one atom thick.
On top of that, Logan's claws can cut through nearly anything, including the skin of beings like the Hulk. Piercing Superman's flesh would be difficult but far from impossible for Wolverine, making the Man of Tomorrow vulnerable to every slash and stab attack Logan lands on him.
Can Wolverine's claws cut Captain America's Shield?
Captain America's Proto-Adamantium shield was left unscathed by Wolverine's claws, as it would be in most comic cases. The MCU and X-Men Universe versions of the characters, on the other hand, would have a very different battle of metal.
It is not so much that Magneto cannot affect vibranium, but that the metal's vibratory nature and energy-absorption components can be harnessed in such a way that the Master of Magnetism meets his match.
