How to reverse the glitch:
1. Do the 2nd tutorial so that you spawn with 2 Altairs.
2. Die
3. While it is loading, plug in the extra controller.
4. You should spawn with only one Altair, and not be in the start of the level.
5. Go back and kill everyone.
6. Go forward and kill everyone until you reach the end of the level.
7. Congratz, you can now finish the level and/or the game!