Answer:
That was the most worst movie I have ever seen.
Step-by-step explanation:
The most worst is an incorrect form of superlative of BAD, as the worst is already a superlative, or 3rd form of bad. Using most with worst is excessive and not necessary. The most form is usually used with the adjectives and adverbs, especially those of more than one syllable.
For example the most beautiful, the most disturbing, the most relevant, the most unbelievable, etc.