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