Never shown onscreen, but enemy mechs are shown exploding so it's possible this happens to their pilots. One ending has you set an inhabited planet on fire.
There is a certain point in the game where the player is knocked unconscious for more than a few days. There is another where the player has a near-death experience.
There are multiple endings and the game expects you to play through all of them. Each ending seeks to raise more questions than they answer, and have an emotional pull.