Basically everyhting u asked if i want is a yes but it can't be no girl painted with spray paint to resemble a robot figure and for the last part would I be wrong If I said I dont mind that?
As usual,
Monster Girl Quest is the first game on any list involving monster girls. MGQ and its sequel
MGQ: Paradox both have plenty of very monstrous girls, although the most monstrous ones in MGQ are all in part 3. It's usually safe to assume that all of the really weird ones are either drawn by Xelvy or Delphinus. Aside from that, there aren't many stories that can match up to MGQ even outside of porn games.
Butterfly Affection is a short VN about raising a worm thing you found in front of your house. It's very short but also very cute, it's one of my personal favorite short stories.
SHRIFT is like Undertale in a lot of ways but with a lot more reverse rape. There are some pretty good designs here in my opinion and it's overall a pretty good game. I highly recommend playing the easiest difficulty, the game may get frustrating otherwise. My biggest criticism with the game is that the spider girl isn't nearly as cute as Muffet.
Castle of Temptation is pretty fun. One of the four levels is themed entirely around spooky doll girls and there's a few robots in the third level. If you want monstrous monster girls, the frog things in the third level absolutely fit the bill. I really wish there was even a single scene with one of the fairies.
Monster Girl Dreams mostly just has cosplay-tier girls, but there are a decent amount of more monstrous designs too. Most of them are slimes, but there's some other stuff too.
Setalia the Demon Realm and
Seal of Lutellaria have some pretty spooky designs and are pretty fun side-scrolling games.
I haven't played
My Dystopian Robot Girlfriend much and it's not finished yet, but it's cute.
I haven't played any of the Violated Hero games yet, but
Violated Hero II has a harpy and a robot girl in the preview pictures so I'm pretty sure it's amazing.
I haven't played
Anomalous Coffee Machine, but there seem to be some pretty interesting transformations in the preview pictures.
Nursery Slime seems cute but I haven't played this one either.
Rainy Day Doll Love - NTR RPG in love with a doll - and
You must be registered to see the links
are about doll girls which I think is pretty neat, but neither of them are translated.
I'm not a xenophile so I don't know about any games like that other than Teraurge (although I'm pretty sure that's the only one anyways) but some of Xelvy's designs in MGQ: Paradox probably count.
There are quite a few games involving a female protagonist getting fucked by animals, monsters, aliens, or insects but I assume those aren't quite what you're looking for.
I can think of a few games where girls are monsters in the metaphorical sense, but I assume those don't count either.
Notable mentions go to
OOZEHAZARD and
Mika's Happiness Medicine. While I wouldn't call any of the girls in these games monster girls in the traditional sense, both of them have what I'd consider to be absolutely amazing body horror considering how much they disgust most people.
That's pretty much all I can think of for now for things involving notably monstrous monster girls, although I skipped a few that only had a single token slime girl or something like that. I'm sure there are quite a few that I don't know, haven't played, or simply forgot about though.