Frank Castle has never been anything close to a "superhero." Besides not having any special abilities to speak of (okay there was that one time he was an angel, but we can forget about that), The Punisher started out as a Spider-Man villain. It was only by sheer force of will of the fanbase that he began starring in his own comics and attained "anti-hero" status.
That said, Frank still has it in the bad guy department. We see as much in Jason LaTour and Robbi Rodriguez' comic series Spider-Gwen, which centers on a Marvel Universe in which Peter Parker died and Gwen Stacy was the one to suffer the bite from that radioactive spider. In this world, Daredevil is a bad guy, Captain America is an African-American woman and Frank Castle is one of those "loose cannon" cops that will do anything to get the job done.
Though in a certain light this Punisher could still be a rootable protagonist in the vein of Jack Bauer, Captain Frank Castle is the one tasked with bringing down Spider-Woman, who has mistakenly been blamed for Peter Parker's demise. Pitting Castle against a comic's titular heroine makes him less of a Dirty Harry-ish "He's a wild card... but he gets results!" cop and more of a power-mad police officer that eerily reflects today's headlines.
That isn't to say Captain Castle is altogether unlikable. When ninjas make him drop his donut, you feel his pain. You want those ninjas to pay for keeping the Punisher from his pink sprinkles.
Though not the star of this book by any means, Spider-Gwen's version of The Punisher shows that the core concept of a character hellbent on justice has a lot of versatility.
Leave it to the 90s to push that flexibility to the limit.
Let's get this out of the way: Punisher 2099 isn't a good comic. It's a terrible comic, or depending on how you look at it, a terribly great comic. Whereas titles like Spider-Man 2099 and Doom 2099 were highlights of Marvel's futuristic universe of books, Punisher 2099 took everything about that world to the extreme. And this was the 90s, so "extreme" means labrador-sized laser rifles wielded by bulging muscles belonging to a living grimace with a ten-pack barely restrained by numerous pouches and shoulder pads.
There were plenty of comics like Punisher 2099, but Pat Mills, Tony Skinner and Tom Morgan came up with something a little different. Pretty much every issue has one or more moments so ludicrous that it makes you wonder whether the creators are in on the joke -- like the scene above, when Punisher jumps out a window and says "I don't need a jetpack -- ALL I NEED IS HATE!" This could very well be what's considered a "stealth parody" that is much easier to spot now than it was a couple of decades ago. It's tough to take this guy seriously when he responds to a question about his age with the answer "Thirty-six... CALIBER!"
Hell, this future Punisher's name is "Jake Gallows," which is about as subtle as someone called "Tom Guillotine" or "John Punishington, Esq." His origin story is just as much of a stretch -- he supposedly finds Frank Castle's last war journal, in which the original Punisher entrusts whoever so finds his kill-diary to carry on his work. As it happens, Jake's whole family has just been slaughtered by no-good-niks. And so begins the strange and bizarre journey of Punisher 2099.
Jake's adventures are about as delightfully stupid as you expect -- including detours involving a golden robot and a silent/invisible/sentient motorcycle buddy -- but it goes to a whole other level when Jake Gallows becomes the Director of SHIELD.
See, for a brief period in the 2099 universe, Doctor Doom became President of the United States. One of his first acts as Doctor Dictator was to make Jake the head of SHIELD, heretofore known as the Punishment Police. If you think this makes Jake sound like a bad guy... it sort of does. After straddling the line between hero and villain for the duration of the run, Punisher 2099 goes full-on heel. In Jake's mind, turning the country into a police state is the best possible way to curb crime.
This of course is an obvious overreach of his powers, especially when new laws mean that children as young as seven can be tried (and almost definitely punished) as adults at the tender age of seven and a half.
If this sounds absolutely insane and absolutely obliterates a line that Frank Castle would never cross himself... well, you're probably right. But that's why comics are great! You can take a serious character, plop them in a dystopian future and suddenly you've got a pseudosatire that takes an ordinary premise into a far-flung extreme -- and it works, because you can always lean back on your original character when you're done with the experiment. Any hero can do it, so long as they have a cheesy name replacement.