Here is the full list of all 28 MeltDown achievements.
Own all weapons.
Destroy 30 bots with the Shocker.
Reach 100% Critical Strike with the Fury skill.
Destroy an enemy of each type.
Destroy The Electrocutioner
Destroy The Enforcer
Destroy 30 bots with the Flamer.
Destroy 30 bots with the Grenade or Rocket Launcher.
Get Level 3 Prestige
Collect 100 Chips.
Collect 5000 Coins.
Complete 10 online games.
Do a Multi-Kill.
Destroy 1000 bots.
Get Level 1 Prestige
Max out all skills.
Finish an online game with 4 players.
Obtain a 3 star rank on a mission.
Finish an online game.
Destroy The Barrager
Upgrade a weapon to the maximum level.
Pickup 10 Nukes.
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.