Here is the full list of all 24 Mini Ghost achievements.
Obtain card 3
Destroy a boss in less than 40 seconds
Find night vision goggles
Obtain card 2
Find secret room
Beat the game without dying.
Obtain card 4
Beat the game
Buy everything available
All items in inventory
All hp bar unlocked
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 2 with a laser
Destroy boss zone 3 with a mine