There were a few moments in Marvel's Civil War that put Captain America to the test. One such event involved Frank Castle, aka, the Punisher, and it wasn't your typical ordeal where one man proves the other was wrong through their own actions. Rather, they take a beating in an expression of irony.
When Cap is beginning to marshal his forces for the coming conflict, he is approached by a couple of guys named The Plunder and Goldbug. They were villains who sought to reform themselves by joining up with Cap's band of superheroes who opposed the Superhero Registration Act.
Before they had a chance to do anything, Punisher unloaded on them, killing both men instantly. After all, killing bad guys is what the Punisher does, and when two walked right up and presented themselves, it was like serving them up on a silver platter to the bitter soldier.
Cap didn't appreciate what happened, and he immediately turned on Castle. He beat him relentlessly, but Castle refused to raise a finger in his defense. Captain America is a hero to Castle, and he was more than happy to take a beating from the man. The thing is, Castle was unarmed at this point, which means Cap was pummelling an unarmed man, nearly to death, all the while calling him a "Murderous piece of trash."