any manga that features a bad guy/ villain who falls in love?

Ones I've read:
Hot Gimmick
Threads of Time
Jewels
Princess (lala/ tor)

thanks!

Hanatsukihime
Owari to Hajimari no Miles

Canon

Can't Lose You

Watashi no Ookami-san - Demon Lord falls in love with a hero (though he doesn't seem very evil). Their story is continued in volume 3 of dear, which isn't complete.

Akuma na Eros - Satan himself

Go Go Heaven!! The grandson of the King of Hell falls for Snow White (Shirayuki) (comedy)

Haou Airen Yakuza leader falls for ordinary girl (shoujo smut drama)

you should try Superior although the role of the bad guy is reverse. The heartless demon lord (a girl), falls for the hero who was sent to kill her since she had killed thousands of people. She is very powerful but hide her true self from him and making him fall for her. 😀

Akuma de Sourou not actually evil, more like "hot gimmick"
Seimaden

Go to work, send your kids to school;
Follow fashion, act normal;
Walk on the pavement, watch T.V.;
Save for retirement, obey the law.
Repeat after me: I am free.

Devil Devil;
Hajimete no Aku

Akuma na eros is probably the best example of this.

Akuma no Ororon

Cesare from Kakan no Madonna. Oh, my...

And Silver (FUJITA Kazuko), of course.

Edit: And if you don't mind BL, Let Dai is so totally what you're looking for. In fact, if you don't mind BL, there are tons of titles I could recommend... But this would be the first. You don't even normally have to like BL - it's just an awesome story.

tartufo- I don't mind if it's BL at all, you can make BL recs, I've read all of your recs, kakan no madonna is still not fully translated though, except Silver... can you give me a brief summary about the evil guy in love in Silver and how it happens...ect, but don't give away too much, thanks!