There have been maybe six important Punisher writers and they have very different takes on the character.
Gerry Conway, who created the Punisher, never intended him to be anything but a superhero version of Mack Bolan.
Frank Miller, who used the character as a foil for Daredevil and Spider-Man, clearly disliked the Punisher and thought he was maybe half a chromosome away from being an out-and-out psycho.
Steven Grant, who snapped the character up on a rebound from the “shooting litterbugs” story cited earlier (Bill Mantlo?), tried to rehabilitate him as a straight-up adventure hero in his first solo (limited) series.
Mike Baron, who scripted Punisher’s first ongoing series, seemed mainly fascinated by the moral ambiguity of vigilantism. One of his finest moments was when Belasco (One of Marvel’s Satan stand-ins) taunts him with “Hey Frank, how many innocents have you unintentionally killed? Here’s a hint: It’s more than ten and less than a hundred!” He also had Castle deliver a classic Mike Baron line: “If I paid taxes, I’d be outraged.”
Chuck Dixon, the other major Punisher series scripter in the 90s, chiefly used Punisher to highlight the contrasts between military and civilian culture. This was done to particularly good effect in Dixon’s short-lived Marvel Knights team book (“A woman, a blind guy and me. Guess who’ll do most of the heavy lifting?”)
Garth Ennis had two shots at the character, first as a really violent Warner Brothers cartoon (“Welcome Back, Frank”) and later as an incredibly grim and mostly humorless vigilante under the MAX imprint. I’d say Ennis is the best of the bunch, but he kinda lost me when he had Frank kill Microchip. Again.
Punisher’s a pretty complex character and not everyone at Marvel knows how to write him. The series with angels and a glowing tattoo on his face really missed the point. I think it was Mark Gruenwald who pointed out that if you or I were to suddenly fight crime, this is the way we’d do it: with guns and stuff you can mostly snap up at an army surplus store. Handled correctly, he’s one of Marvel’s best characters.