Here is the full list of all 26 Jamsouls achievements.
Win the first Challenge match
Kill 3 players in arena mode without touching the floor ! That will look pretty cool
Kill 3 players in arena mode with one soldier
Burn friends with a rocket jump, in the game, not in real life
Kill frogs with a certain style
Kill 3 players in one go with a sugar, they'll probably hate you after that
Finally you invited some friends to play this game !
Kill 3 players in arena mode with one bomb
Win a foot match with a gap of 5 points
Kill the first 4 bosses
Win a game with 4 other human players playing with the keyboard
Score a point with the fly in Capture the flag
Kill someone bigger than you
Get all the bronze medals, I'm sure you can do better
Get all the silver medals, not too bad :)
Get all the gold medals, ok now I'm impressed !
Kill your self in a silly manner
Kill 3 players in arena mode with one cactus
You were really close to trigger your super attack !! But...
Win a basketball match with a gap of 5 points
Kill 10 times in a single game with the spike trap !
Get your first gold medal !
Get all the double bronze medals
Get all the double silver medals
Get all the double gold medals
Find out how to play with the hope in multiplayer