Here is the full list of all 30 Gunpowder achievements.
Destroy 12 Bonus Items
Destroyed 50 innocent cacti in your trophy-lust
Destroy a bonus item after destroying the Safe
Received a time bonus on a mission
Destroy 500 destructible objects
Find a hidden trophy
Blow up a safe, destroy all the bonus items, and find a hidden trophy in a mission
Destroy all Cacti, bonus items, and the safe in Mission 1-6 in one playthrough
Destroy 4 walls with a single explosion in Mission 2-23
Beat Mission 3-8 with all Bonus items by only making 8 Switch Track changes
Beat Mission 4-24 with all bonus items by only making 3 turntable changes
Collect all bonus items in Chapter 1.
Collected all bonus items in Chapter 2
Collect all bonus items in Chapter 3
Collect all bonus items in Chapter 4
Collect all trophies in the game
Sweep up gunpowder in a single mission 5x
Detonate the plunger without igniting anything
Blow up Incendio's shack
Complete mission 4-25
Destroyed Boss Grimshaw's symbol of oppression
Beat Mission LOST-6 with all bonus items without the spark being extinguished by a wagon
Break the safe on Mission LOST-12 right before the flooding water washes it away
Beat Mission LOST-21 with all bonus items, without breaking a single crystal
Score a basket on Mission LOST-23
Collect all piggy banks in chapter 5
Collect all hidden trophies in chapter 5
Destroy the safe and all piggy banks in Mission 5-20 without the waterfall extinguishing the fire
Destroy the snowman horde in Mission 5-9 and complete the level
Spare the snowman in Mission 5-6