The battle royale takes place after the bell tower/church scene. Venom (at least I think) captures MJ, forcing Spider-Man to come out and face him. Spider-Man sees what Venom can do and goes to Harry and asks him to come and help save MJ.
If that is so then it means that spidey/peter fights venom before the battle royale meaning 2 fights with venom. Because I highly doubt spidey would run away just from seeing venom and even less he would ask harry for help unless he has sufered venom's raw power firsthand. So maybe peter rushes at venom somewhere(maybe before eddie kindnaps MJ) and gets his butt kicked and then when MJ is taken away by eddie/venom peter realizes that he needs help to defeat venom and then he'll come to harry.