Here is the full list of all 50 Black Maou & Rainbow Kingdom achievements.
Complete Prologue
Complete every trophy
Playtime reaches 2 hours
Complete Exercise Field
Player reaches level 30
Main Base reaches level 9
Kill 1000 enemies
Stage battling time over 3 minutes
Soul reaches 666
Use Poison Gas Bomb
Use Magic Eye Laser
Use Black Holy Light
Use Meteor Shower
Use Black Hole
Proceed to ending
Conquer Kingdom of Red
Conquer Kingdom of Orange
Conquer Kingdom of Yellow
Conquer Kingdom of Green
Conquer Kingdom of Blue
Conquer Kingdom of Indigo
Conquer Kingdom of Violet
Obtain Red Crystal
Obtain Orange Crystal
Obtain Yellow Crystal
Obtain Green Crystal
Obtain Blue Crystal
Obtain Indigo Crystal
Obtain Violet Crystal
You don't say…
All minions reach level 3
All minions reach level 4
All minions reach level 5
SyouMei joins battle
Resurrect more 666 deads
Summon more then 60 minions on the same stage
Use Poison Gas Bomb for 100 times
Use Magic Eye Laser for 100 times
Use Black Holy Light for 100 times
Use Meteor Shower for 100 times
Use Black Hole for 100 times
Clear every stage using only minions
Clear every stage using only Demon King
Red Princess yields up
Orange Princess yields up
Yellow Princess yields up
Green Princess yields up
Blue Princess yields up
Indigo Princess yields up
Violet Princess yields up