Complex sentence: Nick Fury's fight with the unknown monster, is noticed by Johnny Storm and Spider-Man, who are patrolling nearby, they intervene to help Fury and end the fight, once defeated the creature flees.
Split into simpler sentences: Nick Fury's fight with the monster is noticed by Johnny Storm and Spider-Man, who are patrolling nearby. They intervene to help Fury and end the fight; once defeated the creature flees.