Okay, I'll moderate my Moon Knight and Punisher opinions. I hate them as people, but they can make for good contrasts to far better characters. From reading wiki summaries and skimming the artwork on old 70s and 80s Spider-Man issues, I know that Punisher basically started as a side character for Spider-Man to both cooperate and clash with. Punisher wasn't really shown as a heroic protagonist until he got mainstream colour comics, I think. And that didn't happen until 1985, when he was embraced by the public (for some reason). But Punisher with Spider-Man might barely work, in the sense that this maniac with an armoured battle van and an arsenal of weapons makes for good action. He's still not someone I'd ever want to read about in solo stories, though.
Now, as for Moon Knight...Moon Knight is interesting. I still don't understand the character, but I see that he's equally violsnt. Accidentally found a modern comic picture where he skinned someone's face. It's disturbing, and I don't think that image is gonna vanish from my mind easily. But Moon Knight feels like The Punisher, in that they're both crazy action guys who only work for me when their crazy is neutered by better and more moderate characters. Spider-Man, The Defenders, The Thing, even the Werewolf by Night probably keeps Moon Knight in check sometimes. But solo stories? I don't wanna read it. It's a personal taste thing, but these violent characters with insane morals don't do it for me.
Honestly, Punisher and Moon Knight feel like more mainstream versions of Steve Gerber's Foolkiller. The original Foolkiller in Man-Thing was fascinating. This religious nutcase of a young man, he lost his mind when he learned his mentor was immoral and eventually chose to become a serial killer for all those whose "foolishness" ruined america. But then he has a shard of glass impale him in the chest. The glass came from the cryo chamber where he kept the dead body of his mentor, by the way. Foolkiller is nuts, but he feels like a better condemnation of the violent vigilante. He's just a right wing religious serial killer, and it's clear that he thinks of everyone besides himself as a "fool." So he was willing to cleanse all of earth, if he hadn't ended up dying first. He was nuts. And now there's still new foolkillers, although none can rival the original one in pure evil morality.