Here is the full list of all 100 Hentai Unlimited achievements.
Complete 8 puzzles from a fifth artist
Collect 50 bronze medals
Collect 30 silver medals
Collect 30 bronze medals
Collect 25 gold medals
Collect 20 gold medals
Collect 20 silver medals
Collect 15 gold medals
Collect 15 bronze medals
Collect 10 gold medals
Collect 10 silver medals
Complete 8 puzzles from a fourth artist
Complete 5 puzzles from a fifth artist
Complete 8 puzzles from a third artist
Complete 5 puzzles from a fourth artist
Complete another puzzle
Complete 2 puzzles from a fifth artist
Complete 100 puzzles
Complete 5 puzzles from a third artist
Complete 90 puzzles
Complete 2 puzzles from a fourth artist
Complete 80 puzzles
Complete 2 puzzles from a third artist
Complete 70 puzzles
Complete 8 puzzles from a second artist
Complete 60 puzzles
Complete 5 puzzles from a second artist
Complete 8 puzzles from the same artist
Complete 5 puzzles from the same artist
Complete 50 puzzles
Complete 40 puzzles
Complete 30 puzzles
Complete 2 puzzles from a second artist
Complete 20 puzzles
Complete 10 puzzles
Complete 2 puzzles from the same artist
Complete one puzzle