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