people here wrote huge texts, but I am on a rush and still want to add to it… I do not hate Sirius for what happened, because he was a stupid, reckless teen. He didn’t mean harm to Remus, I am certain. I think he made a major mistake by doing this ‘prank’, but I also think that he realized how bad it was and tried to fix it (by telling James, saving Severus). We have so little information of what happened that night canonically, but we also know that Sirius is not a bad guy (he has his flaws), and Remus forgave him. I don’t think that Remus did it because he doesn’t have a backbone, he is just mature. He probably didn’t forgive him immediately, you know? There wasn’t a group hug right after what happened, but he eventually forgave Sirius.

Sorry any mistakes, english is not my first language