First appearance of the Punisher
The Punisher's interactions with Spider-Man in his very first appearance...
What's interesting about this story is that, as others have pointed out, there's no indication whatsoever that the reader's meant to view the Punisher as an anti-hero instead of as another straight-up Marvel hero. There's certainly no indication that Spider-Man has a problem with his methods.
J. Jonah Jameson wants pictures of this new Punisher fellow who's been waging war on the mob, so Peter's trying to find him as Spider-Man. Unbeknownst to him, the Punisher's met the Jackal and been convinced by him that Spider-Man murdered Norman Osborn.
Spider-Man escapes, though the Punisher thinks he's killed him.
Later on, Spidey tracks down the maker of the Punisher's spear-gun through its armorer's plate...
Notice that Spider-Man clearly understands that the Punisher kills people, yet he never demonstrates any outrage or even discomfort over that fact. Their interaction here reads like your typical "heroes get into a fight over a misunderstanding" scenario that superhero writers are fond of and Gerry Conway is especially fond of. At the end of the story, there's no sign that he's concerned or worried about the Punisher walking away free.
It seems pretty clear that Conway didn't intend for the Punisher's willingness to kill to be seen as particularly immoral here, to either the readers' or to Peter's eyes. He's written as a straight-up heroic figure. I'm really curious as to when writers did start portraying his actions in a negative light and writing other superheroes as condemning them.