Here is the full list of all 57 Star Wars Knights of the Old Republic II: The Sith Lords achievements.
Acquire all Light Side Powers
Side with the Queen on Onderon
Install HK-47's unique module
Have Persuasion over 30
Reduce a companion's Influence to zero.
Listen to HK-47's definition of love.
Teach the Handmaiden the ways of the Force.
Recruit Mira
Recruit the Handmaiden
Complete the game on the Light Side
Reach maximum Light Side points
Acquire all Dark Side Powers.
Win a Pazaak game with a full board
Side with the Settlers at Khoonda
Change your mind about siding with the Settlers at Khoonda
Claim Darth Nihilus' mask.
Defeat Nihilus
Learn Force Sight
Learn Moving Meditation
Deduce G0-T0's identity
Break Hanharr's spirit
Learn how to kill Jedi from HK-47
Complete the game on the Dark Side
Defeat Sion
Reach Player Level 30
Have 30 points in Stealth
Have your character replace any of the Sith Lords on the main menu screen.
Kill all the Jedi masters
Side with Vaklu on Onderon
Have 30 points in Demolitions.
Have 30 points in Treat Injury.
Flee Korriban after fighting Sion
Get this by starting the "Trapped" Quest on Korriban.
Loot a body on Korriban
Fill the Party Selection screen
Recruit the Disciple
Get the named Lightsaber crystal
Gain a Prestige class
Convince Vogga the Hutt to sell fuel to Telos.
Recruit Hanharr
Contruct your first Lightsaber
Reach maximum Dark Side points
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.
Repair the damaged droid on the Ebon Hawk
Collect 10,000 credits
Complete the Prologue
Complete the Handmaiden Battle Circle
Destroy Peragus Astroids
Complete the Mandalorian Battle Circle
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