Threshold

"Threshold" is an episode of Star Trek: Voyager that is almost universally regarded as the worst Star Trek episode ever.

Why It Sucks

They describe Warp 10 as an "infinite speed", but they expect to achieve it by using a special form of dilithium in their warp drive. No amount of funky dilithium will allow the ship to generate the infinite amount of energy that would be needed to propel the ship to infinite speed.
Travelling at Warp 10 causes Tom Paris to start mutating, a process that the Doctor describes as Tom undergoing millions of years of "evolution" in a matter of hours. This is utterly absurd, because not only does evolution occur over generations instead of in individual organisms, Tom's mutations should at least be adaptations to his local environmental conditions, which they clearly aren't.
The characters keep contriving reasons to say "threshold" over and over and OVER.