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