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