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