>>11059489SAW Viper from the 108 issue is just random guy who is okay with killing POWs. Lots of soldiers are like that if they can get away with it. Happens all the time in military conflicts. He was basically a nothing character.
Never read what happened with him in later series, but i can't imagine him being anything but random villain you'd see in a Punisher comic. Even his Overkill version is so generic.
And Punisher has no problem with working with others. It's other people that have a problem with him. Characters like Wolverine has problems working with others because he can potentially attack you and talk shit for a laugh. Punisher isn't a jerk and is actually pretty considerate (616 anyway), ditching his teammates if he doesn't think they'll work out.
If you just want a guy with a high body count, that's Snake Eyes or any helicopter/jet dude. Stalker might come close, who also matches the Punisher in terms of professionalism.
