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