In the Marvel Comics and the Marvel Cinematic Universe (MCU), the concept of the multiverse allows for the existence of different versions of characters in alternate universes. While there have been various alternate versions of Captain America depicted in comics and other media, including some with different moral alignments, an "evil" Captain America is not a commonly recognized or prominent character in Marvel lore.
In the mainstream continuity, Captain America is typically portrayed as a virtuous and heroic character, upholding justice and fighting for the greater good. However, in alternate universes or "What If?" scenarios, different versions of Captain America have been explored, some of which might have contrasting motivations or ideologies. These variations can range from morally ambiguous versions to outright villainous counterparts.
It's important to remember that the specifics of characters and their variations can change over time due to new storylines and interpretations. So while an evil Captain America may exist in some alternate reality within the multiverse, it's not a core or widely recognized aspect of the character in the primary Marvel continuity.