It has recently been announced that Frank Castle's The Punisher will be joining Matt Murdock's Daredevil in Daredevil Season 2, releasing next year. This is awesome for me, because I don't know much about The Punisher, but I love Daredevil, so his arrival will finally give me a look into the character. I do, however, know a little about the backstory of The Punisher. From what I know, after Frank Castle's family was murdered after witnessing a mob execution, he decided to become a ruthless, bloodthirsty vigilante who was okay with killing anyone and everyone who got in his way. This kind of ruthless behavior seems like a perfect reason why Daredevil would come into contact with The Punisher. Here is one of my theories as to how, specifically, they will come into contact with one another.
1) The Punisher Is After Kingpin
The Punisher's family was killed by a mob. The Kingpin was Daredevil's main villain in season 1. The Kingpin was, and will most likely be again, the largest crime lord in New York City. My theory is that maybe Kingpin is responsible for the death of The Punisher's family. That would provide adequate reasoning for The Punisher to come to Hell's Kitchen. Say that he comes to Hell's Kitchen to kill, or torture anyone who was connected to his family's death, including Kingpin. If The Punisher stays true to his extremely violent ways from the comics, then he will most likely kill anyone of those people on the spot. That will cause a major problem for Daredevil in New York, causing him to hunt down The Punisher. Obviously, The Punisher is not going to stand for that, so the two of them will become enemies. However, I think that at some point The Punisher will try to break into the prison that Kingpin is in and try to kill him. Daredevil shows up to stop him, but in the process, Kingpin manages to escape, which will give them a reason to team up and stop Kingpin. The two of them join forces and take down Kingpin, maybe even for good. Over time, The Punisher will be influenced by Daredevil's ongoing desire to help people, and be a better person, with a few rough edges of course. We can not have The Punisher going all Steve Rogers on us.