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