Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Good Job (40 points): Complete all missions on Normal or higher game difficulty.
It Slices! It Dices! (10 points): Upgrade a sword.
Enter the Way of the Ninja (10 points): Upgrade Ninjutsu.
How Ya Like Me Now?! (10 points): Complete a Todomé attack.
Yes, I Am That Good. (10 points): Achieve a 10 Hit Combo.
Not Too Shabby (10 points): Achieve a 3 Kill Combo.
Let Off Some Steam (10 points): Use the Cyclone Shuriken to put out a fire.
Burn, Baby, Burn (10 points): Use the Flame Shuriken to set an enemy on fire.
Lightning Strikes Twice (10 points): Use the Lightning Shuriken to charge the surface of water and shock an enemy.
I'm Rubber and You're Glue (10 points): Deflect an enemy's projectile.
Nothing Left But the Dying (10 points): Complete a Finish Attack.
Chewy on the Inside (10 points): Destroy a piece of armor.
Gotta Get Them All (10 points): Find a Shinobi Moji.
Sharp Dressed Man (10 points): Find an outfit.
Bling or Flair? (10 points): Find an emblem.
Hattori Hanzo Achievement Award (20 points): Upgraded all swords to their maximum level.
Snatch the Pebble (20 points): Upgraded all Ninjutsu to their maximum level.
I Think I'll Go for a Walk (30 points): Max out the Health Gauge.
"Feel it flow through you." (30 points): Max out the Chi Gauge.
Almost There (15 points): Find 50% of the Shinobi Moji.
Complete Set (30 points): Find all the Shinobi Moji.
Walk-in Closet (30 points): Collect all the outfits.
Brings Out Your Eyes (30 points): Collect all emblems.
Ya Can't Touch This (15 points): Deflect 20 projectiles.
One with the Blade (15 points): Kill 25 enemies with the Finish Attack move.
Mission.001: Speed Demon (15 points): Complete Mission 001 within 30 minutes.
Mission.002: Master of Style (15 points): Complete Mission 002 with more than 20 Finish Attacks.
Mission.003: Hit Combo Fever (15 points): Complete Mission 003 with a Max Hit Combo above 30.
Mission.004: Ninja Sky Marshall (15 points): Complete Mission 004 with less than 30% jet plane damage.
Mission.005: Nick of Time (15 points): Complete Mission 005 within 40 minutes.
Mission.006: You Want Some? (15 points): Complete Mission 006 with a Max Kill Combo above 10.
Mission.007: Back in a Flash (15 points): Complete Mission 007 within 50 minutes.
Mission.008: Only a Flesh Wound (15 points): Complete Mission 008 without taking 1000 points of damage.
Mission.009: That Just Happened! (15 points): Complete Mission 009 without retrying.
Ninja School Valedictorian (75 points): Achieve a Total Play Result A+ ranking.
Musashi's Way (50 points): Complete all missions on Hard or higher game difficulty.
Your Work Is Done (20 points): Complete all missions without retrying.
A Perfect 10 (20 points): Achieve 10 "Perfect" button presses in a row during a Quick Time Event.
"...And that's all I need." (20 points): Complete all missions using only one of the swords to attack.
Showboat (20 points): Achieve a 100 Hit Combo.
Show-off (20 points): Achieve a 50 Kill Combo.

Additionally, there are nine secret achievements:

Only a Ninja Can Stop a Ninja (25 points): Completed Mission 001 on any difficulty.
Two-Wheel Daredevil (25 points): Completed Mission 002 on any difficulty.
Family Ties (25 points): Completed Mission 003 on any difficulty.
In the Event of an Emergency... (25 points): Completed Mission 004 on any difficulty.
There's Always a Bigger Bug (25 points): Completed Mission 005 on any difficulty.
Oni Hanzo (25 points): Completed Mission 006 on any difficulty.
Deja Vu (25 points): Completed Mission 007 on any difficulty.
Prepare for Glory (25 points): Completed Mission 008 on any difficulty.
Pass the Torch (25 points): Completed Mission 009 on any difficulty.