If this thread were purely about the worst episode, I would judge Precious Cargo as the bottom of the barrel for Enterprise. However, in terms of the most disliked, I have to go with These Are The Voyages..., and here's why.
Precious Cargo is completely and utterly awful, but at the end of the day it's a stand-alone episode that has no real effect on the larger Star Trek canon. These Are The Voyages... not only usurped the spot of the series finale from the far better Demons/Terra Prime two-parter, it also destroyed the character development of damn near everyone in the main cast, then sidelined them in favour of two characters from an entirely different show, and for good measure killed off one of Enterprise's "big three" characters in the most asinine, underwhelming manner possible.
And worse still, had it not been for the success of the Kelvin movies, which in turn resulted in Discovery and the subsequent relaunch of the TV side of the franchises, this dumpster fire of an episode might well have been the last piece of televised Star Trek any of us ever saw.
So yeah, sorry for the essay, but that's why I have to say that TATV is my most disliked episode, and give the point to save Precious Cargo.
"PRECIOUS CARGO" - 1
"THESE ARE THE VOYAGES..." - 1