Full list of all 50 Mortal Kombat achievements worth 1,000 gamerscore. It takes around 300-500 hours to unlock all of the achievements on Xbox 360.
Perform every fighter's forward and backwards throws
Gain Mastery of 1 Fighter
Complete 200 Versus matches (online OR offline)
Win 100 total Online Matches
Unlock Mileena's 3rd Alternate Costume
Complete all Test Your Might mini-game challenges
Complete all Test Your Sight mini-game challenges
Complete Arcade Ladder on max difficulty without using a continue
Discover and fight Hidden Kombatant 1 in Arcade Ladder
Discover and fight Hidden Kombatant 3 in Arcade Ladder
Discover and fight Hidden Kombatant 4 in Arcade Ladder
Discover and fight Hidden Kombatant 2 in Arcade Ladder
Successfully land every playable fighter's X-Ray attack
Unlock all Alternate Costumes
Complete Arcade Ladder with All Fighters
Unlock 100% of the Krypt
Complete all Test Your Strike mini-game challenges
Get all MK Dragons in Test Your Luck
Perform a 10-hit combo with any fighter
Earn 2500 Respect Points via king of the hill matches
Complete 100 Online Matches
Win 10 Ranked Online Matches in a row
Comeback with under 10% health in an Online Ranked Match
Earn 1000 Respect Points via king of the hill matches
Win 10 king of the hill matches in a row
Win A Ranked Online Match without jumping
Win both rounds with timer running out in an Online Ranked Match
Win an Online Match
Get a Flawless Victory in an Online Match
Perform 8 throws in an Online Ranked Match
Complete Arcade Ladder with Any Fighter
Complete Arcade Ladder without blocking (allowed to continue)
Win Arcade Tag Ladder with robot Sektor and Cyrax
Perform 1 of each type of "-ality"
Perform any fighter's hidden finishing move
Unlock 50% of the Krypt
Complete 25 Tower missions
Complete Tutorial Mode
Perform a Fatality!
Complete Fatality Trainer
Complete Story Mode 100%
Unlock Hidden Fighter "Quan Chi"
Spill 10000 pints of blood
Unlock Hidden Fighter "Cyber Sub-Zero"
Complete Story Mode 50%
Perform and land a Tag Combo
Perform a Fatality with all playable fighters
Gain Mastery of All Fighters
Complete all Tower missions
Perform every fighter's hidden finishing move