So if Superman had sex with Lois Lane...
He might kill her...
Even if he was gentle, and took it slow, when he ejacuates, we can assume he has no more control over the speed of those little buggers than a normal man...
Therfore, let's assume he ejaculates at a conservative 5,000 feet per second... that's more than twice the speed of a rifle bullet....(remember "faster than a speeding bullet") probably giving them enough force to blast a whole in her big enough to pass a baseball through...
Let's not even think of her performing oral sex....
This could all be rectified with a kryptonite kondom!
My sexual super-power would be the ability to not only synchronize when both she and I would orgasm at the same time, but to also warp time in a sense to either bring hers on sooner, or to delay mine.