Here is the full list of all 27 Halfway achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Complete the game's main story.
Complete all optional missions in one single play-through (progress resets when starting a new game).
Recycle loot to gain 1000 energy.
Have the team storage at full capacity.
Survive a fight with only one of at least three character fit for action.
Have all characters join your team.
Gina Nia joins your team.
Kill four or more enemies in one turn with all characters.
Jenna Wallace joins your team.
Subject 13 joins your team.
Have five characters join your team.
Dr. Schaffer joins your team.
Kill 100 enemies.
Have the backpack at full capacity with at least three characters.
Josh Connor joins your team.
Loot and empty 50 containers.
Kill 20 enemies.
Kill two enemies in one turn with the same character.
Samuel Lankford joins your team.
Complete an optional mission.
Kill an enemy at full health with a single ranged attack.
Loot and empty 10 containers.
Carefully listen to conversations without interrupting them.
Kill Johannsen, or what's left of him.
Linda Carter joins your team.
Kill 500 enemies.
Find the hidden cake.