I've seen a few YouTube videos with the title 'all endings' for Battleblock. I decided not to watch these until I manage to get it unlocked on my own playthrough.
My thinking is that it's probably one of these:
- Get an A++ on all stages
- Do all time-trials
- Complete the game on insane mode
- Free all prisoners
- All of the above?? =,[
If you don't know of any alternative endings but have done these then that's probably just as informative.
Otherwise, if there really is another/more ending(s), how do you unlock it/them?