Here is the full list of all 57 Star Wars Knights of the Old Republic II: The Sith Lords achievements.
Have your character replace any of the Sith Lords on the main menu screen.
Complete the game on the Dark Side
Acquire all Dark Side Powers.
Kill all the Jedi masters
Install HK-47's unique module
Side with Vaklu on Onderon
Listen to HK-47's definition of love.
Change your mind about siding with the Settlers at Khoonda
Recruit the Disciple
Learn how to kill Jedi from HK-47
Deduce G0-T0's identity
Break Hanharr's spirit
Reach maximum Dark Side points
Recruit Hanharr
Learn Moving Meditation
Reduce a companion's Influence to zero.
Destroy Peragus Astroids
Reach Player Level 30
Complete the game on the Light Side
Defeat Sion
Claim Darth Nihilus' mask.
Defeat Nihilus
Have 30 points in Treat Injury.
Have 30 points in Stealth
Have 30 points in Demolitions.
Acquire all Light Side Powers
Side with the Queen on Onderon
Have Persuasion over 30
Fill the Party Selection screen
Complete the Mandalorian Battle Circle
Side with the Settlers at Khoonda
Get the named Lightsaber crystal
Teach the Handmaiden the ways of the Force.
Flee Korriban after fighting Sion
Get this by starting the "Trapped" Quest on Korriban.
Loot a body on Korriban
Beat the champ on Nar Shadaa
Convince the "champ" to lose the game without playing.
Convince Vogga the Hutt to sell fuel to Telos.
Repair the damaged droid on the Ebon Hawk
Gain a Prestige class
Contruct your first Lightsaber
Recruit Mira
Have 30 points in Repair.
Have 30 points in Computer Use.
Learn Force Sight
Reach maximum Light Side points
Recruit the Handmaiden
Complete the Handmaiden Battle Circle
Get your first Dark Side points
Win a Pazaak game with a full board
Collect 10,000 credits
Let the Sith destroy the Peragus Asteroids
Kill all Sith troopers before they can board the Ebon Hawk
Dance for Vogga
Get your first Light Side points
Complete the Prologue