Here is the full list of all 20 Sonny achievements.
Level up an item to max level.
Complete Patient Zero Zone.
Complete Landfall Zone.
Complete Mutation Zone.
Complete Into the Fire Zone.
Complete The Hidden Forest Zone.
Complete Angel of Light Zone.
Complete The Ghost Baron Zone.
Complete The Hornest's Nest Zone.
Defeat Vileclaw without using the basic Strike ability.
Use your Regenerate ability on an ally.
Deal 100,000 damage in a single hit.
Beat the game only using the Physical tree.
Use all evolutions at least once.
Beat the game without respecing your skills.
Evolve the same skill 3 times in a single fight.
Execute a basic attack 200 times.
Gain 5% bonus damage from 3 different strains.
Defeat the War Lizard without using a single attack.
Defeat Leon the Inquistor without using any allies.