I had a few ideas for achievements. Maybe others have more that can be posted below?
"Higher Education" - Research every tech in the game
"Apes Together Strong" - Complete the game having researched nothing but the story research
"Immovable Object" - Complete the game having lost 0 Xenonauts
"1%" - Have $10,000,000
"Garage Sale" - Sell $1,000,000 worth of items
"Zookeeper" - Capture 1 of every alien
"Purging Squad" - Deploy a squad in which every member is wearing Colossus power armour