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