Here is the full list of all 24 Mini Ghost achievements.
Reach boss zone 1 without killing any monster or being damaged by them
Change a friend's character while he/she is playing
Kill boss zone 3 receiving no damage from it
Destroy boss zone 3 with a mine
Kill boss zone 2 receiving no damage from it
Kill boss zone 1 receiving no damage from it
Destroy boss zone 1 with a rocket
All items in inventory
Beat the game without dying.
Beat the game
Buy everything available
All hp bar unlocked
Find secret room
Obtain card 4
Obtain card 3
Destroy boss zone 2 with a laser
Find night vision goggles
Destroy a boss in less than 40 seconds
Obtain card 2
Find all Twitch Friends
Pick up any item in less than 16 seconds
Beat the game in less than 45 minutes
Beat the game without using secondary weapons
Beat the game without dying or being assisted by doctors