Garth Ennis' stint on the Punisher might've given us some kooky moments over the years, but there's no denying it carried a sense of gravity when it had to.
One story-arc that best exemplifies this actually takes place in the first volume of Punisher Max. Said arc, called 'In the Beginning', features Frank Castle as he attempts to outmanoeuvre both the mob and an off-the-books black ops team, one that features Micro in a somewhat antagonistic role.
Ennis is afforded plenty of room to manoeuvre too, as the book is set outside of the typical 616 timeline. Not only did this allow him to depict violence in a heavily-stylised manner, it also allowed him to tell the Punisher story that he wanted to - one that revisited the character's origins and fundamentally rewrote the sense of pathos that had carried him so diligently since that first meeting with Spider-Man in 1973.
It's a really important book, and while other storylines like Born and Valley Forge, Valley Forge undoubtedly have their merits, you have to go back to the beginning, to get a sense for where it all started.