It was building towards the character's full entrance all season and Daredevil season 2 episode 13 finally unleashed The Punisher. The Punisher has always been a "hero" who stands apart in the Marvel universe since he tends to just shoot villains in the head than attempt to bring them to justice. The Punisher's true identity is Frank Castle, a Vietnam vet who becomes a vigilante when his family is killed by the mob. He was introduced as a Spider-Man villain, but due to his popularity, he eventually earned his own series.
While The Punisher feels like a concept well suited to live-action movies, the character had a famously difficult time on the big screen. Dolph Lundgren (Creed II) first played Castle in 1989's The Punisher, and while it was an entertaining b action movie, it ended up going straight to video in the U.S. The character was rebooted with Tom Jane's Punisher in 2014, but while the actor nailed the role, the shoddy script and jarring tonal shifts hurt the final product. Finally, Ray Stevenson (Rome) took the mantle for Punisher: War Zone, a gleefully over the top, neon-drenched action movie. It's regarded as a cult classic now, but it bombed upon release.
After three failed attempts to turn The Punisher into a movie franchise, Jon Bernthal was cast as the character in Daredevil season 2. The show reimagines Frank Castle's origin somewhat and in keeping with Matt Murdock only donning his Daredevil suit in the season 1 finale, Castle doesn't actually become the Punisher until the end of the season. Bernthal's Frank was considered a major highlight of season 2 due to the actor's powerful performance, which is why Netflix almost immediately greenlit a spinoff show.
In hindsight, the character doesn't actually appear all the much during Daredevil season 2, and Castle's arc finds him slowly coming to embrace the Punisher mantra. Once he learns of his former commander's betrayal in episode 12, he kills the man and raids his arsenal. He comes across an old bulletproof vest and using his old X-ray scan as inspiration, he spraypaints a skull logo on it. In Daredevil season 2 episode 13 "A Cold Day In Hell's Kitchen," Castle wears the vest as he saves Daredevil during a battle with the Hand, before returning to his old home. He makes peace with the loss of his family and burns down the house while planning to track down the last surviving gang members involved in the shooting in Central Park that claimed them.
Daredevil season 2 was always designed as an origin for the Punisher, so it wasn't a big surprise the show waited until the finale to unleash him. Still, it was very satisfying to see Bernthal wear the famous skull and embrace the character's destiny. Sadly, the showrunners behind The Punisher series decided to backtrack a little, and still have Frank in the process of becoming the vigilante. The show was still a great showcase for Jon Bernthal's take on the character, where he added a lot of depth to a character that can easily become one-dimensional.