There was a great article in one of the science fiction magazines; I think Larry Niven wrote it, entitled, IIRC, "Man of Steel, Woman of Putty." It dealt with the problems Superman might have in a relationship with a normal human female, Lois Lane or whoever.

The gist of it was that, even if he had enough control over his voluntary actions not to hurt her, what about his involuntary ones?

The first attempt to consummate their relationship would blow the top of her head off.

Peter.