I literally just woke up, so I read that as "forcing him to cum against a wall" and imagined this in an alley, with Credence pinned by neck and wrists with black smouldering tendrils, shuddering, teeth gritted and moaning desperately as he spurts in his pants.
Re: Obscurus/Credence- forced orgasms, non-con, possession, pain kink
Either way, I love this prompt.