51 Achievements
Air Show Perform 2 aerial gestures before touching the ground in co-op
527 achievers
Asking for Trouble Taunt GLaDOS in front of a camera in each of the five co-op courses
222 achievers
Bridge Building Complete all test chambers in the Hard-Light Surfaces co-op course
455 achievers
Bridge Over Troubling Water Complete the first Hard Light Bridge test
832 achievers
Can't Touch This Dance in front of a turret blocked by a hard light bridge in co-op
265 achievers
Confidence Building Complete all test chambers in the Mass and Velocity co-op course
561 achievers
Door Prize Examine all the vitrified test chamber doors
216 achievers
Drop Box Place a cube on a button without touching the cube
535 achievers
Dual Pit Experiment Do the same test twice
656 achievers
Empty Gesture Drop your co-op partner in goo while they are gesturing by removing the bridge under them
147 achievers
Final Transmission Find the hidden signal in one of the Rat Man's dens
207 achievers
Four Ring Circus Enter 4 different portals without touching the ground in co-op
127 achievers
Friends List With Benefits While playing co-op, hug 3 different people on your friends list
108 achievers
Gesticul-8 Perform all 8 gestures of your own volition in co-op
390 achievers
Good Listener Take GLaDOS' escape advice
530 achievers
High Five Celebrate your cooperative calibration success
753 achievers
Iron Grip Never lose a cube in Chamber 6 of the Mass and Velocity co-op course
107 achievers
Lunacy That just happened
631 achievers
Narbacular Drop Place a portal under your co-op partner while they are gesturing
185 achievers
No Hard Feelings Save a turret from redemption
602 achievers
Obstacle Building Complete all test chambers in the Excursion Funnels co-op course
386 achievers
Overclocker Complete Test Chamber 10 in 70 seconds
155 achievers
Party of Three Find the hidden companion cube in co-op test chamber
123 achievers
Pit Boss Show that pit who's boss
251 achievers
Portal Conservation Society Complete Chamber 3 in the Hard-Light Surfaces co-op course using only 5 total portal placements
90 achievers
Portrait of a Lady Find a hidden portrait
276 achievers
Preservation of Mass Break the rules in Test Chamber 07
566 achievers
Professor Portal After completing co-op, complete Calibration Course online with a friend who hasn’t played before
118 achievers
Pturretdactyl Use an Aerial Faith Plate to launch a turret
257 achievers
Rock Portal Scissors Win 3 co-op games of rock-paper-scissors in a row
239 achievers
SaBOTour Make a break for it
758 achievers
Scanned Alone Stand in a defective turret detector
571 achievers
Schrodinger's Catch Catch a blue-painted box before it touches the ground
181 achievers
Ship Overboard Discover the missing experiment
296 achievers
Smash TV Break 11 test chamber monitors
123 achievers
Stalemate Associate Press the button!
750 achievers
Still Alive Complete Course 4 with neither you nor your co-op partner dying
53 achievers
Stranger Than Friction Master the Propulsion Gel
678 achievers
Talent Show Never lose a cube in Chamber 6 of the Mobility Gels co-op course
64 achievers
Tater Tote Carry science forward
689 achievers
Team Building Complete all test chambers in the Team Building co-op course
646 achievers
The Part Where He Kills You This is that part
633 achievers
Triple Crown Solve 3 co-op chambers in the Mass and Velocity course in under 60 seconds each
86 achievers
Tunnel of Funnel Master the Excursion Funnel
631 achievers
Undiscouraged Complete the first Thermal Discouragement Beam test
920 achievers
Vertically Unchallenged Master the Repulsion Gel
718 achievers
Wake Up Call Survive the manual override
980 achievers
White Out Complete the first Conversion Gel test
664 achievers
You Made Your Point Refuse to solve the first test in Chapter 8
259 achievers
You Monster Reunite with GLaDOS
929 achievers
You Saved Science Complete all test chambers in all courses of co-op
336 achievers