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