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