If you like seeing a character evolve on the page, read Barracuda.
At the start of his eponymous story arc in Punisher MAX #31-36, he's not really himself yet. The Barracuda we know and love is a happy-go-lucky, perpetually grinning wall of muscle, like a black equivalent of the Russian from Welcome Back, Frank. He's funny because he'll cheerfully hang out with anyone and have jolly, goofball reactions. (Even if committing ultra-violence.)
When he first appears, though, he's not that. He's usually scowling. Goran Parlov soon realised that the happier he drew Barracuda, the funnier the character became... but the guy was still just a gangland thug, albeit a ridiculously huge, depraved one who's done jobs in places like Africa.
Here, though, Ennis has given the character his own solo mini-series. (He'd been going to kill Barracuda at the end of his first appearance, but his editor asked him to bring him back.) Ennis likes soldiers... and so now Barracuda used to be in the U.S. Army, is a former Green Beret and did black ops for the CIA in Latin America, assisting in coups and regime change. He knows Oliver North. I'm not complaining or anything. It fits. We know the CIA did things like that and used people like him, obviously. It does, though, very much give the impression of a character who's been evolving in mid-story.
Anyway, this story is fun. It's not the serious tone of Punisher MAX. It's a goofy comedy with art to suit, as Parlov plays with varying degrees of cartoonishness. One of the first things Barracuda does is beat the hell out of the mobsters from The Sopranos, while the baddie is "Big Chris" Angelone, who's basically Christopher Walken. The haemophiliac gangster son is silly as hell, both in art and concept, as is the very funny death of a certain cocaine-running dictator.
Oh, and I love the joke of all those children watching as Barracuda inserts a .357 Magnum in a Soprano anus.
The plot has lots of evil people scheming to backstab, kill, overthrow, etc. each other and get rich selling lots of cocaine. This includes Barracuda, obviously. This story contains no good people. There's ultra-violence, a million flying bullets and a punchline that's either referring to fellatio or cannibalism. (Or possibly both.) There's also a dumb Donald Trump look-a-like who used perform sexual favours for Barracuda in prison, although this story was published ten years before Trump became US president. You don't need to read this series and it's in no way essential to anything, but it's a laugh.
(Mind you, Ennis made Barracuda a lot more serious again for his Punisher MAX return in Long Cold Dark...)