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