They have teamed up in some comic storylines. It often happens when the situation demands their combined skills and powers to overcome a powerful adversary.
Perhaps in the fanfiction, the Punisher is initially mistaken for a criminal by Spider - Man. Spider - Man tries to stop him from what he thinks is a brutal act of vigilantism. But as the story unfolds, Spider - Man discovers that the Punisher is actually targeting a really bad guy who has slipped through the legal system. This leads to a complex relationship where Spider - Man has to decide whether to support the Punisher's actions or try to bring him to justice in his own way.
Neither might be more dominant overall. In a well - written fanfiction, they would balance each other out. Spider - Man can bring in the aspect of hope and redemption, while the Punisher can represent the harsh reality of crime - fighting. Their interactions would be a give - and - take, with neither truly overpowering the other in all aspects. For instance, in a fight against a group of thugs, the Punisher might take out some with his guns, but Spider - Man could save the day by rescuing hostages and preventing collateral damage.
It all starts when Peter Parker gets bitten by a radioactive spider. This gives him amazing powers like super strength, the ability to climb walls, and a 'spider sense'.
The Punisher, or Frank Castle, was a normal guy with a family. His military background gave him a set of skills that were both useful and deadly. Once his family was massacred, he snapped. He turned his skills towards punishing those who he thought deserved it. His origin story is one of tragedy and a thirst for justice outside the normal bounds. He doesn't wear a colorful costume like some superheroes. Instead, he has a simple skull emblem on his chest, representing death to those who do wrong.
It's very important as it likely contains the whole narrative of Spider - Man. It could include his origin, all his battles, and character development, giving fans a comprehensive view of the character.
It could be his mentor. In the fanfic, the mentor might think that Spider Man is becoming too powerful and is a threat to the balance of power. So, he could betray Spider Man by leaking his secret identity or setting him up to be captured by the authorities.