Here is the full list of all 23 A Building Full of Cats achievements worth 1,000 gamerscore.
Find Fofiño
Find all hidden cats in the first floor
Find all hidden cats in the second floor
Find all 50 cats in the fourth floor
Find all 50 cats in the first floor
Find all 50 cats in the second floor
Find all 50 cats in the third floor
Find all hidden cats in the third floor
Find all hidden cats in the fourth floor
Find all 50 cats in the fifth floor
Find all hidden cats in the fifth floor
Find all 15 cats on the roof
A big tail, indeed...
Find Fofiño!
Adopt a cat!
I see you!
You can't hide!
Find all hidden cats in the bunker
Find all cats in the bunker