Here is the full list of all 30 Asterix & Obelix XXL 2 achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Stop Caesar's invasion plan
Reach 100% completion
Find all the postcards
Finish all challenges at Gold rank
Beat the Caesars
Find all the diamond helmets
Acquire all available upgrades
Buy all the figurines
Beat every type of Roman
Free Suchafuss
Find all the diamond helmets on a level
Open the door on Pirate Island
Find out who Getafix really is
Beat 30 Romans in Fury mode
Discover the fake Gaulish village
Beat 2500 Romans
Pull the lever on the underground level
Free Kerosene
Bullseye!
Beat 100 Romans under the effect of a magic potion
Gain access to LuckSore
Collect 9999 helmets
Free Battermix
Obtain x6 multiplier
Gain access to Venitia
Buy a figurine
Buy an upgrade
Finish a challenge at Gold rank
Stun 10 Romans at once
Enter Las Vegum