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