Here is the full list of all 27 Stay Silent achievements.
Eliminate 1 opposing player by any means
Eliminate 50 opposing players by any means
Eliminate 300 opposing players by any means
Eliminate 1,000 opposing players by any means
Win a game in 1v1 mode
Win a game in 2v2 mode
Win 10 games
Win 100 games
Win 500 games
Win 3,000 games
Eliminate 10 players using a Colt M1873, a Stevens 311R, or any other firearm
Eliminate 50 players using a Colt M1873, a Stevens 311R, or any other firearm
Eliminate 200 players using a Colt M1873, a Stevens 311R, or any other firearm
Eliminate 10 opposing players with grenades
Eliminate 50 opposing players with grenades
Eliminate 200 opposing players with grenades
Complete the tutorials
Win a game in the Church level
Win a game in the Graveyard level
Win a game in 1v1 mode without killing anyone
Eliminate 2 opposing players in a 2v2 game
Win a game in 2v2 mode without killing anyone
Hold out to the last moment and win a game with no more than 10% HP left
Win a game with full HP
Use 66 Alien Masks
Win a game after killing at least one opposing player with a Revolver and bullets and without using any damaging items, skills, or other weapons
Reveal opposing players with an Electro Trap 25 times