Here is the full list of all 40 Rex Rocket achievements.
Defeat the Waste-Bot.
Collect 15 ammo expansions.
Destroy 1000 terra-oozlings.
Obtain the jet pack.
Defeat the Commando-Bot.
Collect 5000 energons.
Defeat the Slime-Mech.
Collect 15 health expansions.
Obtain grenades.
Talk to 100 NPCs.
Defeat the Electro-Bot.
Preform 200 charge jumps.
Collect 40 info nodes.
Defeat the Enforcer-Bot.
Die 25 times.
Get crushed.
Defeat the Slime Boss.
Die from spikes.
Die in acid.
Find all 18 missing records.
Find all 3 missing books.
Defeat 5000 terra-oozlings.
Defeat 1000 helperBots.
Defeat 5000 helperBots.
Collect 80 info nodes.
Defeat a boss without taking any damage.
Complete the game and become a hero again.
Complete the game without using a continue.
Complete the game in less than 3 hours.
Complete the game without dying more than 10 times.
Obtain every weapon in the game.
Find the Grenade Launcher.
Find the Tracking gun.
Find the Boomerang.
Find the Air-Talarias.
Collect all 40 health expansions.
Collect all 7 grenade expansions.
Defeat the Teleport-Bot.
Defeat the Crusher-Bot.
Defeat LAUREN.