Here is the full list of all 18 HangTogether achievements.
Guess any Letter 100 times
Guess any Letter 500 times
Guess any Letter 1,000 times
Guess any Letter 5,000 times
Guess any Letter 10,000 times
Guess any Letter 15,000 times
Guess any Letter 20,000 times
Guess any Letter 30,000 times
Win over 9,000
Win a round without making a guess
Win a round in 5 seconds or less
Win a Round in any Category
Play a game with a Friend
Successfully guess an 8 letter word
Successfully guess a 3 letter word
Lose 100 rounds
Lose 500 rounds
Lose 1,000 rounds