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