Whole new meaning to: "That's my secret, Captain. I'm always angry."

There was a moment when Captain America and The Punisher met, and it was kind of a collision of the Greatest Generation & Gen X truth regimes.

Frank Castle was a veteran of Vietnam. Had grown up reading stories about Captain America, and decided to enlist and fight for his country. In doing so, he was turned into a weapon by a government far more cynical and malicious than the one he'd grown up understanding. He was betrayed and abandoned by the institutions he trusted, and eventually the only institution he had left was his family; whom criminals murdered. The government itself seemed to have no qualms in working with these killers, let alone letting them run wild. So Punisher exists to bring them hell to pay.

Captain America sees Punisher as a raving lunatic, a terrorist, and a serial killer. Steve Rogers is a highly upstanding moral figure who, even when betrayed by these institutions, holds to the highest moral code. He, himself, was a weapon made by the same cynical government, but never let himself get dragged to the depths of cynicism and depravity that Frank Castle did. As a result, Steve Rogers despises Frank Castle. And Frank Castle thinks of Steve Rogers as the hero that he wished he could have been, but is now yet another loss and betrayal. Except, in his own way, Castle is still a highly moral figure, and wouldn't dare attack or betray Rogers. They have very different lines they refuse to cross, but those lines are there.