The the Punisher does have a superpower, and it’s just as depressing as fans might expect.
In 2013’s Thunderbolts Annual #1 by Ben Acker, Ben Blacker, and Matteo Lolli, the Thunderbolts (consisting of Red Hulk, Venom, Elektra, Deadpool, the Leader, and the Punisher) are on a fairly shocking mission: kill Doctor Strange. Stephen Strange had seemingly lost his mind during the events of this comic, rampaging through the city in manic hysteria wearing nothing but his Cloak of Levitation, the Eye of Agamotto, and blue underwear. Worse yet, Strange was casting spells on everyone around them, using his magic to make everyone happy. While that sounded good on the surface, nothing could be further from the truth.
The Punisher was one of the first of the Thunderbolts who not only knew Doctor Strange needed to be stopped (no matter how good his spell seemed on the surface), but was also really the only antihero who could kill him - especially since their target wasn’t actually Doctor Strange at all. Their target was actually a demonic Old One named Oberoth’m’gozz impersonating Doctor Strange. So, Punisher borrowed Ghost Rider’s hellfire shotgun and blew Oberoth’m’gozz away. How did he get close enough to do that? Well, that has to do with his superpower: the Punisher can’t be happy (except when he’s killing, and that’s just for a moment).
The Punisher Has the Most Depressing ‘Power’ in Marvel Comics: He Can’t Be Happy
The Punisher’s Inability to be Happy is Powerful on an Otherworldly Level
It’s true that the only thing that makes the Punisher happy is killing, which is how he was able to get close enough to Oberoth’m’gozz to blow the demonic Old One away with Ghost Rider’s hellfire shotgun. However, the Punisher also itted that killing only makes him happy for a fleeting moment, it doesn’t bring him lasting, genuine happiness. And, honestly, that felt like more of a badass line one says before killing someone anyway, as even killing doesn’t actually make the Punisher happy. He kills because that’s who he is - like a Terminator or something - not because he derives sick joy from it.
So, if killing is the only thing that makes the Punisher feel even a hint of happiness (and even that is a stretch), then that means the Punisher is incapable of feeling happiness - on an otherworldly, supernatural level. All the other of the Thunderbolts were trapped in a spell of happiness by the otherworldly power of the fake Doctor Strange. His magic was too great to resist, and even those who are able to keep their emotions in check - including and especially the likes of Elektra and Venom - were overtaken by the spell. But not the Punisher, which proves that his inability to be happy is literally a superpower.
Unhappiness Isn’t the Only Superpower the Punisher has Ever Had
The Punisher has Been Superhuman on a Number of Occasions
Cosmically-powerful unhappiness is a pretty depressing superpower, but in this case, it really came in handy, as it gave the Punisher the extra edge he needed to stop the fake Doctor Strange and save the world. However, that’s not the only time the Punisher has had superpowers in Marvel Comics - far from it, in fact. When the Punisher was brought back to life after being sliced to pieces by Wolverine’s son, Daken, he became Frankencastle who wielded the power of the Blood Stone. On a separate occasion, when the Punisher was being hunted by demons, he aligned himself with the angels of heaven and gained angelic powers.
More recently, the Punisher was chosen by the evil ninja clan, the Hand, to wield the power of the Beast - the demon they worship. Every person he killed made him more powerful, just as it grew the hellish power of the Beast itself. Speaking of hellish power, the Punisher (in an alternate reality) once made a deal with Mephisto after he was murdered by Thanos to come back from the dead as the new Ghost Rider. After some time, Frank Castle’s Ghost Rider became Galactus’ Herald, infused with the Power Cosmic, becoming Cosmic Ghost Rider.

You May Not Agree With the Punisher, But One Dark Scene Converted Most Marvel Haters
The Punisher has had some dark stories throughout the years, but one story in particular took things to a brutal new level.
So, while base-level Frank Castle may seem powerless, the Punisher has certainly been a superhuman on multiple occasions in Marvel Comics. And, secretly, the Punisher has always had a superpower: profound unhappiness - and it’s so powerful that even a Doctor Strange-level super-villain couldn’t defeat it.