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

Sharp Steel (10 points): Complete the Steel Mill on any difficulty level in Tournament.
Hard Steel (20 points): Complete Steel Mill on Insane level.
Splash Down (10 points): Complete Ocean Liner on any difficulty level in Tournament.
Watery Grave (20 points): Complete Ocean Liner on Insane level.
Out on Probation (10 points): Complete Prison on any difficulty level in Tournament.
Hard Time (20 points): Complete Prison on Insane level.
Waterway to Go (10 points): Complete Venice on any difficulty level in Tournament.
Wet and Wild (20 points): Complete Venice on Insane level.
Crate Work (10 points): Complete Warehouse on any difficulty level in Tournament.
A Crate Effort (20 points): Complete Warehouse on Insane level.
A Stately Achievement (10 points): Complete Manor House on any difficulty level in Tournament.
Full House (20 points): Complete Manor House on Insane level.
Defcon 3 (10 points): Complete Bunker on any difficulty level in Tournament.
Bunker Buster (20 points): Complete Bunker on Insane level.
Warlord (30 points): Complete the game on any difficulty level in Tournament.
Skillzone (40 points): Complete Warzone on Insane difficulty
Join the Club (40 points): Play an event with every one of the 6 unlocked characters in either Tournament or Single Event.
The Awards Show (25 points): Achieve one of every "in game award" either in Tournament or Single Event.
Show Off (20 points): Achieve every "in game award" in one level in either Tournament or Single Event.
Save our Souls (20 points): Spell the word SOS in the Warehouse in either Tournament or Single Event.
Listmania (5 points): Save 5 Playlists in GunPlay.
Premium Membership (20 points): Finish a Tournament on any difficulty with all 8 characters.
Rack em Up (10 points): Achieve your first x10 combo in either Tournament or Single Event.
Hidden Treasures (30 points): Shoot All Secret Skullshots in every level in either Tournament or Single Event.
Scavenger (10 points): Shoot All Skullshots on one level in either Tournament or Single Event.
Bag them Bones (30 points): Shoot All Skullshots on every level in either Tournament or Single Event.
Melee the Elephant (25 points): Kill 30 enemies in a level with a melee attack in either Tournament or Single Event.
Combo Killer (30 points): Reach the level objective with a maximum combo in either Tournament or Single Event.
Efficiency (30 points): Kill every enemy on a level using less than 50 bullets in either Tournament or Single Event.
Breakthrough (10 points): Smash 50 Doors in either Tournament or Single Event.
Scores on the Board (10 points): Get in the top 100,000 on any leaderboard.
Tabletopper (25 points): Get in the top 5,000 on any leaderboard in Tournament.
Top Gun (25 points): Get more than 10,000 points for a single kill in either Tournament or Single Event.
Sprint the Gauntlet (20 points): Complete a Run the Gauntlet with 20 seconds left.
SkullMaster (25 points): Hit 5 Skullshots in a row (without killing a bad guy in between).
Welcome to The Club (10 points): Win your first ranked match.
Taking part that counts (10 points): Be on the winning team in a ranked team game.
Capture King (20 points): Capture the base 25 times in Ranked matches.
Club on Tour (25 points): Win a ranked match in every location.
First Blood (20 points): 25 "First Kills" in any Ranked Multiplayer game mode.
Big Game Hunted (20 points): Survive for 120 seconds as the hunted in Hunter Hunted.
Target Man (20 points): Shoot 100 Skull shot targets in Team Skullshot.
Fox Hunter (20 points): Kill the Enemy Fox 25 times in Ranked Matches.
Points Mean Prizes (15 points): Score 10,000 points in a Score Match.
Free For All Elite (30 points): Win any free-for-all game without dying.
Siege Breaker (20 points): Your team survives for more than 2 Minutes in Team Siege.
Demolition Man (20 points): Get 100 Explosive Kills in Ranked Matches.
One Shot (20 points): Get 100 Sniper Kills in Ranked Matches.
Brawler (20 points): Get 100 Melee Kills in Ranked Matches.
No, Seriously (40 points): Kill 10,001 people in multiplayer Ranked Matches.