A female HYDRA soldier forces Steve to have sex with her (whether it's to get pregnant with a super soldier child, just for her perverse pleasure, or whatever is up to the author). Not only that, but she forces him to be the dominant partner and do all the work and fake enjoyment during it. I want to see how he reacts to that, and how he comes to terms with the fact that even though he got it up and came it doesn't mean what she did was OK, it's still rape and not his fault at all.