This is a manga I once saw when I browsed the site, but now I cannot find it.
It is about a male lead, who is either a hero, fallen hero, demon lord or just lord, don't remember. I know there were women attacking him, who of course lose, and he makes them their slaves. As I remember he has a power very similar to Killgrave (the guy from Jessica Jones), he can mind control them, or rather their bodies as they are aware of what's happening. He has intercourse with them if he wants, and like with all of them, they are first embarrassed, then they don't mind. I don't remember if there was an elf among those he controlled. They also somewhat freely keep him company.
Once scene I vividly remember is that they rescue a princess, and the main hero makes a comment about her breasts being of a special kind, new one he did not encounter, nipples to be precise, he called them inverted I think.

So this is basically a harem, fantasy, mature (it's not hentai I think), ecchi

I searched for mangas with maou in title, and there is a similar manga about a dark mage in a dungeon, but he's older and has a succubus (there wasn't one in the manga I'm looking for) and the guy in question is younger. It's also not the one where hero kills the demon lord and makes a pact with a mage in a dungeon (and has sex with his demon maid), collecting manga from negative feelings, such as shame and embarrassment - girls attacking them are falling into traps that are of course sexual.

So please, if someone knows, do tell the title.

It might be:
Himekishi ga Classmate!

Or (less likely):
Class Teni de Ore dake Haburareta node, Doukyuusei Harem Tsukuru Koto ni Shita

What’s the title of the one with the demon maid?

Yep, thanks alot! It was indeed the Himekishi ga Classmate. The one with the demon maid IO cannot remember now, in the first chapter he is fending off assassins sent by the kingdom that doesn't need him anymore after he slayed the demon king, one of the assassins is a girl that he neutralizes, she begs him for her life, to the point she pisses herself, he says it's not very hero like to kill her, she passes out.
I briefly read it to see if it is the one I'm looking for, so I can't say which one was it, but I was looking on manga fox with the help of HakuNeko (very useful tool to download or quickly browse the pages) under the search query "Maou". It has to be one of them, in the first chapter you'll see some assassins trying to kill the former hero (blue was his name?) and there's the scene with the girl peeing and he thinks to himself to go to the former hideout of the demon king he slew, where he happens to meet the mage he slew the demon king with, who proposes a contract to work together. Maybe someone else remembers? I can try to find it later.