Warning: contains spoilers for Captain America/Iron Man #4!
Marvel's worst Captain America story makes a shocking resurgence in Marvel Comics, and not all fans are thrilled with the development. Secret Empire, the infamous 2017 storyline in which Captain America was revealed to be a Nazi, was not well-received by readers, to put it mildly, and the event was so widely derided that Marvel held off on referencing the conflict for years. But Captain America/Iron Man #4 contains a storyline that references the entire storyline, for good or for ill.
In Secret Empire, Steve Rogers' sleeper agent programming takes over and his true allegiance is revealed. He's a Hydra agent and always has been, and moves to put the United States under Hydra (read: Nazi) control. Rogers is still, perhaps unbelievably, written as a "good" person, albeit one who believes that placing the country under an oppressive Hydra regime is the best possible situation for the American people. The 'HydraCap' is revealed to be a creation of the Cosmic Cube, and the real Steve Rogers emerges to battle the Hydra imposter. Though good eventually prevailed over evil, the entire event left a rather poor aftertaste; seeing a character created by two Jews to fight fascism was seen as an incredibly insulting development.
Captain America/Iron Man #4 contains 51, a member of the Fifty-State Initiative implemented in the aftermath of Civil War. The armor serves as a major plot point - 51 wanted to use the Hydra armor to gain access to a supercomputer from Iron Man's past - but it also makes Captain America quite emotional. He clearly would rather forget the armor existed at all, but the current storyline and Marvel editorial have other plans.
It's standard procedure in comics to respond to a universally-loathed story by pretending the events that transpired never transpired at all, and even write the entire affair off as an alternate-universe storyline (the Ultimate line of comics did as much with Ultimate Iron Man's origin). But Secret Empire is a part of Captain America's history, and the storyline ultimately does contain a lesson. Mind, said lesson "Nazis are bad" is admittedly rather simplistic, but is nevertheless (rather unfortunately) a lesson that must be taught and retaught ever few decades or so.
The HydraCap armor exists, but HydraCap himself has yet to make a grand appearance in comics as the next horrifying villain. Perhaps Marvel will let him sit in prison for decades, or perhaps he can even learn from the error of his ways and reform. Nevertheless, Captain America's worst storyline in decades is a part of his history, and those who fail to learn from history are doomed to repeat it.