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