If you ask any fan what their favorite moment was from Avengers: Endgame, most people will tell you that it was when Captain America proved himself worthy and used Mjolnir against the invading Thanos. His worthiness was actually teased all the way back in Avengers: Age of Ultron where the weapon actually moved a bit when Steve tried lifting it, though many fans wondered why he didn't use the weapon during the film's events.
Enter Christopher Markus and Stephen McFeely, the writers of Infinity War and Endgame, who gave a semi-decent explanation as to why Steve wasn't worthy during Age of Ultron. Captain America: The Winter Soldier revealed that Hydra killed Tony's parents and Steve withheld that information from his fellow Avenger. It's a serviceable explanation but still not great since Steve didn't exactly tell Tony through a heart-to-heart conversation.
Captain America's worthiness will probably be questioned by a lot of us but there's no doubt that his use of Mjolnir against Thanos was really amazing. If we're going by the rules of Mjolnir, Steve is a pretty honorable warrior who always does what's right so, in a sense, he is pretty worthy of the weapon. Then again, so are a lot of the other heroes in this universe so I dunno.
Avengers: Endgame is now available on digital platforms and Disney+, along with a number of other MCU movies.