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