Endings

Shared approach

Bio-pod, Escape, and Mercenary all start from the surface after layer 11. I am not reprinting spoken lines. The wiki gives the route and the achievement names, not a transcript I am willing to treat as official dialogue.

Bio-pod

In the lab, follow the scientist through the door on the right. Only a chipped character can take that door, and a chipped character cannot use items in the lab. The achievement named for this ending is Company's Best.

Escape

You must be unchipped and carrying a gun. Wait until the scientist finishes, then shoot. In the operating room the wiki lists a short surgery: anesthetic, major surgical tool, clamps, pull the cargo, take over the line, leave by the door. Reinforcements are listed about a minute later. Killing no guards is the Pacifist achievement. The ending achievement is Company's Worst.

Mercenary

Requires a finished Bio-pod or Escape first, a chipped character, and a fresh run that is not Endless. On layer 1, break the tech ball, take the nanotech scanner, and use it before you leave layer 1. That teaches the merc scarf recipe and grants 200 INT experience. Collect six chips, one each on layers 2, 3, 4, 5, 7, and 9. At 18 INT, craft the merc scarf from a scarf, a circuit board, and the six chips, and carry it to the surface. Achievement: To Be Continued.

Death and character clears

Related achievements named on the wiki: Millions to One for taking the cargo, Cannon Fodder for an Experiment clear, The Marksman for Milky, The Cannibal for Dune. Death itself is not a fourth ending.