Here is the full list of all 25 Asterix & Obelix XXXL : The Ram From Hibernia achievements.
Finish the level in Gaul
Finish the level in Drogheda
Finish the level at the festival
Finish the level at the Hibernian Games
Finish the level at the cliffs
Finish the level in Tara
Get a gold medal
Get all the gold medals for time
Obtain all the collectables
Get all the gold medals for health
Get all the specific gold medals
Get all the gold game medals
Get a gold health medal in a camp in multiplayer
Perform an ultimate attack with each type of item and Roman
Send three Roman soldiers flying at the same time
Destroy 100 breakables
Defeat a Roman by throwing a fish at him
Defeat a Roman with his own shield
Revive an ally by throwing them food
Cancel a dash, throw and charged-attack action
Beat 12 Romans in a single ultimate attack
Beat a Roman after catching a pass
Beat a centurion before he calls for help
Beat a Roman with a musical instrument
Get all the gold medals for score