Finished the main story, full-size inn with every upgrade, every family member, every amenity and maxed them out, got every customer and their preferences.
EXCEPT. The hipster. Does anyone know how do I get them? That quest is starting to irk me seeing that I've gone at least 60 days without a solution to it.
And while I'm at that, does anyone know how to get the Serial Killer achievement? I've already tried demolishing rooms with people in it, and that didn't work.
So you just have to get -10 in the approval! (thumb up)
Demolish all rooms and amenities and unassign all of your workers and play few (like 10 to 20) days to loose approval points all the way down to -10 and you got the freakin' hipster!
Get 8 hipsters and you get threat and with threat you can kill
And as you already knew kill 15 customers and there's your last achievement.
Ok, so I got all the trophies. I don't remember how I got the hipster, but I can tell you can kill customers by demolishing their room when they're inside. If you did it right, you'll see a little ghost appear as part of the demolition animation. After the first kill, the characters at the end of the day will be like OMG did we just do that?
You need a certain number of 0-star ratings to get Hipsters. For Serial Killer, you need to demolish a room while someone is inside of it. This means it must be done during the day, while guests are in the room. If you go after this in a single day, the resulting periods thereafter will likely earn you the zero star ratings you need for hipsters.
You get hipster by "naturally" obtaining zero star ratings from 12 customers. By "naturally," I mean NOT by killing them but from them leaving the hotel with a zero rating. Tip: It is much, much easier to get the zero rating near the beginning of the game.
A very easy way to get zero star ratings later in the game: Instead of rooms just put 2 Amenities on the first floor and replace all alipin rooms with other ones. Set priority of all customers to first floor/alipin and restrict all other rooms. Now all customers will leave the inn without checking in. Beside that approval rating will decrease.