Here is the full list of all 24 Wholesome Slaughter achievements.
Complete A Level Without Taking Damage
Kill 100 Pandas
Complete All Exterminator Achievements
Kill 100 Schwaplops
Pickup Over 100 Ammo Crates
Find Every Secret Present
Kill 100 Unicorns
Die 10 Times
Complete The Campaign In 15 Minutes Or Less
Complete The Campaign Without Dying
Complete Level Four
Defeat The Final Boss
Heal For Over 1000 HP
Jump 300 Times
Kill 100 Wisps
Walk 666 Distance
Complete Level Three
Kill 100 Bears
Complete Level Two
Get A Kill With Every Weapon
Find A Present
First Death
Complete Level One
Kill The Guide Fairy