I was a big fan of the big things come in small packages trope. What're some good stories read where the MC is a bit small for his age is a complete badass in pretty much every other aspect of his life. I'd appreciate if there is a bit of maledom and a harem. The harem doesn't have to be there(is that the correct there to use there?) But I'd like if it was
Living Next Door to Heaven by aroslav comes to mind. Even has the harem, though emphatically no dom of any kind, and improbable tai chi mastery.
Ernest Bywater's 'Odd Man In College' comes to mind. The protagonist is described as somewhat effeminate in appearance, but proves that he is far from that in some of the situations he finds himself.
https://storiesonline.net/s/11052/odd-man-in-college
Lazlo Zalezac's Oscar Meyers. However, he's not a badass everywhere else in life - he's a total disaster in the kitchen (an oft-repeated joke in the story).
I don't know whether it fits your criteria but I vaguely remember a rather good sci-fi romance involving a character who was very short but immensely strong because he came from a world with high gravity. I believe he was the only one of his kind to be enrolled at an academic institution, where he met a female from a very different background. Mining plays a significant part. Unfortunately the author and title elude me - can anyone help?
ETA 'Marianne' by Uncle Jim. Oops. Forget I spoke.
AJ