Captain America (Steve Rogers) is a superhero from the Marvel Comics Universe. Patriotic by name and motives, Cap's loyalty lies with America, and is commonly referred to as "The First Avenger".
Initially failing to meet US army requirements, Steve volunteered for Operation: Rebirth, a project that aimed to enhance soldiers to peak physical fitness through the injection of the "Super Soldier Serum". During one of his missions, he was left for dead and froze in the ice, being thawed out several years later by S.H.I.E.L.D., where he become a member of The Avengers. His signature weapon is his indestructible shield, made out of a Vibranium-metal alloy.
In M.U.G.E.N, Captain America was made by various creators.
MystikBlaze was the very first to make a complete Captain America character for M.U.G.E.N. This version is based on Capcom's Marvel Super Heroes version of Captain America and includes Infinity Gems within the character. If you select the character while holding start the character will change into a Marvel vs. Capcom play style. This version of Captain America is highly regarded as one of the best programmed M.U.G.E.N characters, especially considering it was also one of the first.
This version is made for M.U.G.E.N 1.0. The main difference between this one and the MystikBlaze version is that this Capt includes an intricate shield code that helps to avoid bugs when fighting against other M.U.G.E.N characters, particularly grapplers. This version is based on the Marvel vs. Capcom 2 version of Captain America but maintains the standard M.U.G.E.N 6-button layout.
Kong's Version is also a Marvel vs. Capcom 2 version of Captain America adjusted to a 6-button layout. He has different modes of him, which makes him a unique Captain America than from the other 2, based on their moveset.
Axking made a version using MysticBlaze's Captain America for a base. He added new sprites, although some of the old MvC sprites are still in there. He gave it new moves, like the shield punch, spinning shield, and shield slide. This version of cap cannot lose his shield like MysticBlaze's version. The shield punch has an issue: when it is blocked, it does more damage than if it wasn't blocked.
Ultimate Captain America by Sic-1 is a palette edit of the original Captain America and is recoded so that the shield never leaves Capt's arm except while being explicitly thrown for a moment. He also includes a new set of special and hyper attacks.