In mission 1 obtain H11 in hidden cave to unlock Colorado Rockies MP Arena

Acquire every weapon available in mission 1

Complete mission 1: Colorado Mountains

Complete mission 1: Colorado Mountains on Hard difficulty

Complete mission 2: McKenzie Airbase Interior

Complete mission 2: McKenzie Airbase Interior on Hard difficulty

Complete mission 2 in less than three minutes to unlock Goofies MP Characters

In mission 3 obtain binoculars to unlock Caves MP Arena

Complete mission 3: Colorado Interstate 70

Complete mission 3: Colorado Interstate 70 on Hard difficulty

Acquire every weapon available in mission 3

Complete mission 4: I-70 Mountain Bridge

Complete mission 4: I-70 Mountain Bridge on Hard difficulty

Complete mission 5: McKenzie Airbase Exterior

Complete mission 5: McKenzie Airbase Exterior on Hard difficulty

Complete mission 6: Colorado Train Ride

Complete mission 6: Colorado Train Ride on Hard difficulty

Complete mission 7: Colorado Train Race

Complete mission 7: Colorado Train Race on Hard difficulty

Complete mission 8: C-130 Wreck Site

Complete mission 8: C-130 Wreck Site on Hard difficulty

Complete mission 8 in less than three minutes to unlock Syphon Filter 1 MP Characters

In mission 8 kill Steven Archer with headshot while he attempts to escape to unlock Park Jungle Gym MP Arena

In mission 9 obtain girly mag to unlock Pharcom Incubator Lab MP Arena

Acquire every weapon available in mission 9

Complete mission 9: Pharcom Expo Center

Complete mission 9: Pharcom Expo Center on Hard difficulty

Complete mission 10: Morgan

Complete mission 10: Morgan on Hard difficulty

In mission 11 kill three guards before they shoot down disco ball and throw grenades to unlock Disco Basement MP Arena

Complete mission 11: Moscow Club 32

Complete mission 11: Moscow Club 32 on Hard difficulty

Acquire every weapon available in mission 11

In mission 12 obtain PK-102 from one of the crashed cars to unlock Rhoemer's Bunker MP Arena

Acquire every weapon available in mission 12

Complete mission 12: Moscow Streets

Complete mission 12: Moscow Streets on Hard difficulty

In mission 13 kill guard before he blows up car and obtain BIZ-2 from it to unlock Surreal MP Arena

Complete mission 13: Volkov Park

Complete mission 13: Volkov Park on Hard difficulty

Complete mission 14: Gregorov

Complete mission 14: Gregorov on Hard difficulty

Complete mission 15: Aljir Prison Break-In

Complete mission 15: Aljir Prison Break-In on Hard difficulty

Complete mission 15 without using the crossbow to unlock Aljir Prison MP Arena

Acquire every weapon available in mission 16

Complete mission 16: Aljir Prison Escape

Complete mission 16: Aljir Prison Escape on Hard difficulty

Acquire every weapon available in mission 17

Complete mission 17: Agency Bio-Lab

Complete mission 17: Agency Bio-Lab on Hard difficulty

In mission 18 obtain M-79 in operating theatre to unlock Agency Computer Lab MP Arena

Complete mission 18: Agency Bio-Lab Escape

Complete mission 18: Agency Bio-Lab Escape on Hard difficulty

In mission 19 obtain dirty laundry from washing machine to unlock DC City Park MP Arena

Complete mission 19: New York Slums

Complete mission 19: New York Slums on Hard difficulty

In mission 20 obtain M-79 on top of the car park stairs to unlock Syphon Filter 2 MP Characters

Acquire every weapon available in mission 20

Complete mission 20: New York Sewer

Complete mission 20: New York Sewer on Hard difficulty

Complete mission 21: Finale

Complete mission 21: Finale on Hard difficulty