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