Here is the full list of all 44 Underhero achievements.
You deserve a raise
The End of The World
Defeated ???
All weapon Upgrades!
Spared the Masked Children in Heroes Road
All HP Upgrades!
All Music Cassettes
Recruited the Moth Queen
Recruited The Baron
Eased a Fathers Mind
All missing keys used
Defeated T. Bur
The Show must go on
Read all Robot Text Logs
Night Theater
Defeated El Salserissimo
Cook the spiciest salsa
Complete Jilani'snPepper Collection
Found the Hidden Treasure of the beach
Cleared the Pica Pica Coliseum
Half weapon Upgrades!
Defeated Baron van Gregory
Won the Ice Skating Competition
Completed the Bros Quest
Defeated The Grey Kid
You gave Blobber his favorite drink
Made your first drink
Defeated The Moth Queen, Alexandria II
A tree full of beer
Won the Ant's Gang Race
Defeated Mr. Stitches
First HP Upgrade!
Half HP Upgrades!
First Music Cassette
Half Music Cassettes
First Shield Upgrade
All Shield Upgrades
First missing key used
Finish the Intro
Killed your First Enemy in Combat
Your First Bribe
Killed 20 Enemies
Bribed 20 Enemies
First weapon Upgrade!