UnBEARable Quest:

First, you will meet a girl and she will ask for an antidote. And as a gift she will give you a vegetable.
Second, after getting the vegetables, go to the ruins of the 9th floor (if I'm not mistaken) there are people dying of hunger. Give him the vegetables and you will get an adult book (ero manga).
Third, take the book to the Underground Market and give it to the bald man who lives in a house (right next to the masseur's house). And he'll give you some kind of grilled lizard (sorry if I misunderstood). And this is useful for the ice magician.
Fourth, head to the 33rd floor (hopefully so), and give it to the ice mage. And you will get the love potion.
Fifth, go to floors 36-38 (I forgot the exact location), there will be an adventurer who is attracted to a female spider. Give it to the adventurer and you will get the teddy bear.
Finally, take the teddy bear and give it to the girl who lives to the left of the blacksmith's house (Canton). And you will get a very great necklace.

NB: I know this from the Fabul0usFreak account on Steam Community. Thanks btw~

Unfallen:

Beat the game at 0 depravity.
Attention, always reject or threaten the person, and don't accept the offer. 3 people who should be threatened, namely: the mysterious owner of the antidote (4th floor), the gatekeeper to the Underground Market (beside a cheap inn), and an elderly person who has back pain (36th floor). Hopefully I'm not wrong in providing the location information. Tehee ~

Also, be careful not to get too involved with Goblins, Bardo, Celia and Kiara. Stay away from brothels too, of course.

For other achievements:

Just follow what's on the H-scene room (Hentai scene). And the achievement will reveal itself.