Here is the full list of all 28 MeltDown achievements.
Get Level 3 Prestige
Get Level 1 Prestige
Destroy an enemy of each type.
Destroy The Electrocutioner
Max out all skills.
Collect 100 Chips.
Destroy 30 bots with the Grenade or Rocket Launcher.
Destroy The Enforcer
Complete 10 online games.
Do a Multi-Kill.
Destroy The Barrager
Collect 5000 Coins.
Upgrade a weapon to the maximum level.
Destroy 1000 bots.
Obtain a 3 star rank on a mission.
Pickup 10 Nukes.
Finish an online game.
Destroy 30 bots with the Shotgun.
Destroy 30 bots with a melee weapon.
Complete a mission in less than 2 minutes.
Melee Kill a Fuel Bot.
Complete a mission without losing any health.
Finish tutorial.
Own all weapons.
Finish an online game with 4 players.
Destroy 30 bots with the Flamer.
Destroy 30 bots with the Shocker.
Reach 100% Critical Strike with the Fury skill.