The Punisher is one of the most violent protagonists in the Marvel Universe. Wolverine may have claws that can slice through anything, but he has a code that holds back his bestial ways. The Punisher's code is that he's engaged in a constant war, one that doesn't pause for even a second. As such, writers have often dabbled in the argument about whether the character is just an antihero, or actually a glorified villain, given his methods.
Whether hero or villain, Frank Castle's ability to see the world in black and white has wrought some thoroughly brutal sequences in Marvel's history.
While he has been around since 1974, it wasn't until the 1990s that Marvel Comics truly allowed for different imprints and the official fall of the Comics Code Authority to bring Punisher's brutality to the page uncensored. They made up for lost time with an overgrowing body count, disturbingly detailed art and colorists were scrambling to get the buckets of red ink they needed to fit the high demand.
Consequently, there have been dozens of occasions in the comics where the Punisher has revelled in his style of crimefighting, leading to deaths most Marvel readers couldn't believe made it onto the page in the first place.