Worst movie of all time!

"Bad" is very subjective... sometimes if a movie is extremely 'bad', it can actually be entertaining.
A good example that comes to mind is a sci-fi movie released by Amazon called "The Dawnseeker".
It is hilariously and painfully acted, costumed, and edited. Really quite a masterpiece of tragedy.
I do not recommend watching it sober, as you will most likely need to be intoxicated/high to even slightly enjoy it.