Here is the full list of all 50 Overload achievements.
Kill every operator on Ymir Outpost
Complete the training mission
Complete a Cronus level without killing any operators (Rookie or harder)
Get 100 kills in Challenge Mode Countdown (Hotshot or harder)
Get 100 kills in Labyrinth
Get 500 Challenge Mode kills on Trainee
Get 20 consecutive Challenge Mode kills without taking damage
Get 100 Challenge Mode kills on Insane
Finish 5 Cronus levels without finding any secrets
Score 100,000 in Challenge Mode on Rookie
Score 100,000 in Challenge Mode on Hotshot
Score 100,000 in Challenge Mode on Ace
Destroy every operator in a Lockdown without taking damage (Rookie or harder)
Get 50 Challenge Mode kills in one session without firing a primary (secondary/smash only)
Get 500 Challenge Mode kills on Rookie
Complete Challenge Mode Countdown with 0 kills (Rookie or harder)
Finish a Cronus level flying only backwards (no sliding or forward movement)
Kill yourself with a devastator 10 times
Finish the Cronus mission without upgrading anything
Finish a Cronus level without picking up a single powerup (except keys)
Max out all secondary ammo at the same time
Break every monitor in the Cronus mission
Survive to the end of Countdown (Ace or harder)
Get 100 Challenge Mode Infinite kills on every level (Rookie or harder)
Score 50,000 and survive to the end of all Challenge Mode Countdown levels (Rookie or harder)
Complete the Outer Moons levels
Complete the Titan levels
Complete the Cronus mission (Trinidad ending)
Complete the Cronus mission (Beale ending)
Finish the Cronus mission on Hotshot
Finish the Cronus mission on Ace
Finish the Cronus mission on Insane
Finish New Game+ (Ace or harder)
Recover every cryotube in the Cronus mission
Find every secret in the Cronus mission
Get 40 kills in each secret level in the Cronus mission
Finish the Cronus mission in under 3 hours of playtime without saving
Complete Phoebe Refinery without using the Headlights or Flare
Give the Hologuide a command in 5 different Cronus mission levels
Complete the Cronus mission without using the Hologuide at all
Get 1000 kills in Multiplayer
Finish 10 matches in Multiplayer (matchmaking)
Get a kill with every weapon and missile in Multiplayer
Die 1000 times in Multiplayer
Destroy 1000 operators
Unlock all the Challenge Mode and Multiplayer upgrades and loadouts
Fully upgrade every weapon and missile in the Cronus mission
Smash 10 operators in one level
Destroy an operator using only Flares
Win 25 matches in Multiplayer (matchmaking, team or anarchy)