yeh, of course, man :3
For ideas on Adam's murderer/a villain oc:
-He/she could be a twisted/evil version of one of your current ocs...?
-or maybe they could be one of Adam's bullies from his childhood. (since Bloody said they met the person before and it could fit well with Cherry's involvement in the story)
-Perhaps a family member who has murderous intentions for him due to something that happened in the past....?
-Maybe someone who had a love interest in Cherry before Adam started dating her, and he ended up enraged by the fact that Adam got her instead...?
-Or the person could be a friendly appearing character who befriends the gang and ends up betraying them after he reveals he killed Adam...?
These are 5 ideas I thought of rn. :D