51 Achievements
Air Show Perform 2 aerial gestures before touching the ground in co-op
526 achievers
Asking for Trouble Taunt GLaDOS in front of a camera in each of the five co-op courses
221 achievers
Bridge Building Complete all test chambers in the Hard-Light Surfaces co-op course
453 achievers
Bridge Over Troubling Water Complete the first Hard Light Bridge test
829 achievers
Can't Touch This Dance in front of a turret blocked by a hard light bridge in co-op
264 achievers
Confidence Building Complete all test chambers in the Mass and Velocity co-op course
559 achievers
Door Prize Examine all the vitrified test chamber doors
215 achievers
Drop Box Place a cube on a button without touching the cube
532 achievers
Dual Pit Experiment Do the same test twice
653 achievers
Empty Gesture Drop your co-op partner in goo while they are gesturing by removing the bridge under them
146 achievers
Final Transmission Find the hidden signal in one of the Rat Man's dens
206 achievers
Four Ring Circus Enter 4 different portals without touching the ground in co-op
126 achievers
Friends List With Benefits While playing co-op, hug 3 different people on your friends list
107 achievers
Gesticul-8 Perform all 8 gestures of your own volition in co-op
388 achievers
Good Listener Take GLaDOS' escape advice
528 achievers
High Five Celebrate your cooperative calibration success
751 achievers
Iron Grip Never lose a cube in Chamber 6 of the Mass and Velocity co-op course
106 achievers
Lunacy That just happened
629 achievers
Narbacular Drop Place a portal under your co-op partner while they are gesturing
184 achievers
No Hard Feelings Save a turret from redemption
599 achievers
Obstacle Building Complete all test chambers in the Excursion Funnels co-op course
384 achievers
Overclocker Complete Test Chamber 10 in 70 seconds
154 achievers
Party of Three Find the hidden companion cube in co-op test chamber
122 achievers
Pit Boss Show that pit who's boss
250 achievers
Portal Conservation Society Complete Chamber 3 in the Hard-Light Surfaces co-op course using only 5 total portal placements
89 achievers
Portrait of a Lady Find a hidden portrait
275 achievers
Preservation of Mass Break the rules in Test Chamber 07
564 achievers
Professor Portal After completing co-op, complete Calibration Course online with a friend who hasn’t played before
117 achievers
Pturretdactyl Use an Aerial Faith Plate to launch a turret
255 achievers
Rock Portal Scissors Win 3 co-op games of rock-paper-scissors in a row
238 achievers
SaBOTour Make a break for it
755 achievers
Scanned Alone Stand in a defective turret detector
569 achievers
Schrodinger's Catch Catch a blue-painted box before it touches the ground
179 achievers
Ship Overboard Discover the missing experiment
294 achievers
Smash TV Break 11 test chamber monitors
122 achievers
Stalemate Associate Press the button!
747 achievers
Still Alive Complete Course 4 with neither you nor your co-op partner dying
52 achievers
Stranger Than Friction Master the Propulsion Gel
675 achievers
Talent Show Never lose a cube in Chamber 6 of the Mobility Gels co-op course
63 achievers
Tater Tote Carry science forward
686 achievers
Team Building Complete all test chambers in the Team Building co-op course
644 achievers
The Part Where He Kills You This is that part
630 achievers
Triple Crown Solve 3 co-op chambers in the Mass and Velocity course in under 60 seconds each
85 achievers
Tunnel of Funnel Master the Excursion Funnel
628 achievers
Undiscouraged Complete the first Thermal Discouragement Beam test
917 achievers
Vertically Unchallenged Master the Repulsion Gel
715 achievers
Wake Up Call Survive the manual override
977 achievers
White Out Complete the first Conversion Gel test
661 achievers
You Made Your Point Refuse to solve the first test in Chapter 8
258 achievers
You Monster Reunite with GLaDOS
926 achievers
You Saved Science Complete all test chambers in all courses of co-op
334 achievers