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