Here is the full list of all 40 The Walking Dead: Season 2 achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Made it to the ski lodge.
Met someone on a bridge.
Found a way across the water.
Left the cabin.
Talked to a stranger.
Helped someone through a difficult time.
Completed Episode 1: "All That Remains"
Headed out with the group.
Took care of yourself.
Got what you needed.
Arrived at the cabin.
Met new people.
Found a campsite.
Arrived at the shore.
Settled things with a new friend.
Completed Episode 2: "A House Divided"
Arrived at your new home.
Witnessed a murder.
Made it through your first day.
Committed larceny.
Got beaten down.
Invited some friends into the compound.
Gave what you got.
Completed Episode 3: "In Harm's Way"
Got separated from the group.
Learned new survival skills.
Returned to the meeting place.
Reached the museum.
Found the Observation Deck.
Survived the attack.
Got back on the road.
Completed Episode 4: "Amid the Ruins"
Made it out alive.
Took a breather.
Stopped for the night.
Reached the other side.
Made it through to morning.
Reached the terminus.
Found your way through.
Completed Episode 5: "No Going Back"