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