Here is the full list of all 20 It Returned To The Desert achievements.
Kill 99 Ants
Kit returned
Kill a large ant
Ask for more casserole
Escape the hospital
Find gold in the mines
Congratulate Kenny to his victory
Congratulate Sofia to her victory
Complete 5 lab experiments
Save Glint Rock
Find your destiny in the woods
Score more than 900 points on the target range
Recruit all possible party members within a single game
Save Alex' life
Show the video tape to the mayor
Visit the Annual Spring Festival
Complete 5 tours with the truck
The aftermath
Defeat the ants on the highest difficulty
Talk to Kenny about the crashed UFO