The final boss will be your lesbian alien girlfriend that manipulated you into all of this. See, she ordered the robots to attack planets so you would be forced to seek the ancient robot destroying artifact. She follows you on your quest to find all its four pieces and when you have them, she reveals her true nature: she is the leader of the robots and actually an android that wants to purge the universe from useless meat. With your help she could find the ancient robot destroying artifact and dispose of it- now nothing can stop her. Unless, that is, you defeat her in an epic battle, but first she assumes her true form: her tits grow tentacles/wires, her thighs slide open and reveal they are rocket launchers, her shoulders expand into miniguns and she shoots a deadly, screen-filling laser from her mouth. To defeat her you must activate four switches scattered around in the boss arena while dodging her shots. Those switches lower the force-field that makes her invincible. After that, it's the plasma gun all the way. When she dies, she reverts to her normal form and Shepard (?) holds her in his/her arms, a tear in his/her rugged face. He/she cries out "WHY????", a sad remix of the "love" theme starts playing, the scene fades out, credits.