51 Achievements
Air Show Perform 2 aerial gestures before touching the ground in co-op
412 achievers
Asking for Trouble Taunt GLaDOS in front of a camera in each of the five co-op courses
176 achievers
Bridge Building Complete all test chambers in the Hard-Light Surfaces co-op course
365 achievers
Bridge Over Troubling Water Complete the first Hard Light Bridge test
650 achievers
Can't Touch This Dance in front of a turret blocked by a hard light bridge in co-op
213 achievers
Confidence Building Complete all test chambers in the Mass and Velocity co-op course
453 achievers
Door Prize Examine all the vitrified test chamber doors
179 achievers
Drop Box Place a cube on a button without touching the cube
419 achievers
Dual Pit Experiment Do the same test twice
529 achievers
Empty Gesture Drop your co-op partner in goo while they are gesturing by removing the bridge under them
114 achievers
Final Transmission Find the hidden signal in one of the Rat Man's dens
164 achievers
Four Ring Circus Enter 4 different portals without touching the ground in co-op
96 achievers
Friends List With Benefits While playing co-op, hug 3 different people on your friends list
87 achievers
Gesticul-8 Perform all 8 gestures of your own volition in co-op
316 achievers
Good Listener Take GLaDOS' escape advice
425 achievers
High Five Celebrate your cooperative calibration success
595 achievers
Iron Grip Never lose a cube in Chamber 6 of the Mass and Velocity co-op course
82 achievers
Lunacy That just happened
505 achievers
Narbacular Drop Place a portal under your co-op partner while they are gesturing
147 achievers
No Hard Feelings Save a turret from redemption
483 achievers
Obstacle Building Complete all test chambers in the Excursion Funnels co-op course
311 achievers
Overclocker Complete Test Chamber 10 in 70 seconds
128 achievers
Party of Three Find the hidden companion cube in co-op test chamber
97 achievers
Pit Boss Show that pit who's boss
199 achievers
Portal Conservation Society Complete Chamber 3 in the Hard-Light Surfaces co-op course using only 5 total portal placements
75 achievers
Portrait of a Lady Find a hidden portrait
227 achievers
Preservation of Mass Break the rules in Test Chamber 07
460 achievers
Professor Portal After completing co-op, complete Calibration Course online with a friend who hasn’t played before
96 achievers
Pturretdactyl Use an Aerial Faith Plate to launch a turret
201 achievers
Rock Portal Scissors Win 3 co-op games of rock-paper-scissors in a row
196 achievers
SaBOTour Make a break for it
604 achievers
Scanned Alone Stand in a defective turret detector
460 achievers
Schrodinger's Catch Catch a blue-painted box before it touches the ground
147 achievers
Ship Overboard Discover the missing experiment
235 achievers
Smash TV Break 11 test chamber monitors
99 achievers
Stalemate Associate Press the button!
598 achievers
Still Alive Complete Course 4 with neither you nor your co-op partner dying
40 achievers
Stranger Than Friction Master the Propulsion Gel
546 achievers
Talent Show Never lose a cube in Chamber 6 of the Mobility Gels co-op course
49 achievers
Tater Tote Carry science forward
554 achievers
Team Building Complete all test chambers in the Team Building co-op course
516 achievers
The Part Where He Kills You This is that part
507 achievers
Triple Crown Solve 3 co-op chambers in the Mass and Velocity course in under 60 seconds each
65 achievers
Tunnel of Funnel Master the Excursion Funnel
508 achievers
Undiscouraged Complete the first Thermal Discouragement Beam test
716 achievers
Vertically Unchallenged Master the Repulsion Gel
577 achievers
Wake Up Call Survive the manual override
758 achievers
White Out Complete the first Conversion Gel test
534 achievers
You Made Your Point Refuse to solve the first test in Chapter 8
215 achievers
You Monster Reunite with GLaDOS
724 achievers
You Saved Science Complete all test chambers in all courses of co-op
267 achievers