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