QUOTE(Satou-chan @ Apr 10 2019, 10:21)

Issei Hyoudou
He has a big harem that wants to have sex with him but he never seems to pick that up because he is a dense motherfucker. When you have a big harem consisting of goddesses the first thing you'd do is fuck them, but no, not in Issei's case. He almost got BTFO'd by Phoenix in S1 and almost got his crush stolen away from him. No wonder why there are so many NTR doujins of High School DxD.
Take it you are watching the anime. It is explained later on in the light novels. The reason why he has not slept with any of them is because he respects them too much to take advantage of them (he is not too stupid; just too nice). Also he has insecurity issues which leads him to believe that they are just messing with him and don't mean what they say. This gets sorted out and he realized they do actually like him. By the end of volume 25 he is engaged to like 8 of them with it being noted that it will probably be at least 12 eventually. So he does get his harem. By earning peoples respect. Not by fucking everything in sight. That approach was done in School Days. Did not end well.