Here is the full list of all 28 Asterix & Obelix XXL: Romastered achievements worth 1,000 gamerscore.
Complete stage 1 - Gaul
Complete stage 2 - Normandy
Complete stage 3 - Greece
Complete stage 4 - Helvetia
Complete stage 5 - Egypt
Complete stage 6 - Rome
Complete the entire game in "Easy" mode or at a higher level of difficulty
Complete the entire game in "Normal" mode or at a higher difficulty level
Complete the entire game in "Difficult" mode or at a higher difficulty level
Defeat 200 Romans under the effect of the magic potion
Defeat 5000 Romans
Buy all the combos from the merchant
Get the maximum number of shields
Retrieve all the golden laurels
Complete all the course challenges
Complete a course challenge with more than 5 seconds to spare on the Gold level
Complete all the time challenges
Reach the Gold level in all the time and course challenges
Collect more than 99999 helmets
Spend more than 50000 helmets at the merchant's
Retrieve a golden laurel
Keep the combo gauge full for 60 seconds
Find and defeat Redbeard in each level
Complete all the course and time challenges
Switch between the REMASTER mode and the ORIGINAL mode
As Asterix, strike a Roman tossed by Obelix in midair while under the effect of a magic potion
Sling yourself using rubber bands 20 times in less than 30 seconds