Full list of all 51 Portal 2 achievements. It takes around 20-25 hours to unlock all of the achievements in the base game on Windows.
The base game contains 50 achievements, and there is 1 DLC pack containing 1 achievements.
After completing co-op, complete Calibration Course online with a friend who hasn’t played before
Complete Course 4 with neither you nor your co-op partner dying
Drop your co-op partner in goo while they are gesturing by removing the bridge under them
Complete Chamber 3 in the Hard-Light Surfaces co-op course using only 5 total portal placements
Complete all test chambers in all courses of co-op
Taunt GLaDOS in front of a camera in each of the five co-op courses
Complete all test chambers in the Excursion Funnels co-op course
Find the hidden companion cube in co-op test chamber
Never lose a cube in Chamber 6 of the Mass and Velocity co-op course
While playing co-op, hug 3 different people on your friends list
Break 11 test chamber monitors
Find a hidden portrait
Discover the missing experiment
Examine all the vitrified test chamber doors
Catch a blue-painted box before it touches the ground
Save a turret from redemption
Find the hidden signal in one of the Rat Man's dens
Place a cube on a button without touching the cube
Show that pit who's boss
Use an Aerial Faith Plate to launch a turret
Complete Test Chamber 10 in 70 seconds
Refuse to solve the first test in Chapter 8
That just happened
This is that part
Master the Excursion Funnel
Do the same test twice
Complete the first Conversion Gel test
Master the Propulsion Gel
Carry science forward
Master the Repulsion Gel
Press the button!
Stand in a defective turret detector
Take GLaDOS' escape advice
Make a break for it
Complete the first Hard Light Bridge test
Break the rules in Test Chamber 07
Complete the first Thermal Discouragement Beam test
Reunite with GLaDOS
Perform all 8 gestures of your own volition in co-op
Complete all test chambers in the Hard-Light Surfaces co-op course
Dance in front of a turret blocked by a hard light bridge in co-op
Place a portal under your co-op partner while they are gesturing
Solve 3 co-op chambers in the Mass and Velocity course in under 60 seconds each
Win 3 co-op games of rock-paper-scissors in a row
Perform 2 aerial gestures before touching the ground in co-op
Survive the manual override
Complete all test chambers in the Mass and Velocity co-op course
Enter 4 different portals without touching the ground in co-op
Complete all test chambers in the Team Building co-op course
Celebrate your cooperative calibration success
Never lose a cube in Chamber 6 of the Mobility Gels co-op course