I picked Hatchery, although both Impulse and Future Tense are good, too.
There are so many things about Hatchery on so many different levels. First, there's Archer's increasing devotion to protecting the baby Insectoids, which is creepy, especially when one of them crawls up his shoulder.
Then there's the reaction of the crew to Archer's actions, which they come to believe are jeopardizing their mission in the Expanse.
And finally, there's the division between the Starfleet crew (not just Malcolm!) who know something is wrong with Archer, and the MACOs, who follow Archer's orders blindly to the extent that Major Hayes is put in charge of the bridge after Archer starts confining his officers to their quarters for disobeying or questioning him.
It didn't hurt that at the end of the episode, as Archer is recovering, Hayes starts to show a little genuine respect for Malcolm and the rest of the crew.

(I liked Impulse for the reasons Honeybee cited, and Future Tense because it riveted my attention the first time I watched that episode -- the repetition of scenes which at first I couldn't figure out why they were occurring, and then rooting for Trip and Malcolm to figure out what what was going on as they realized they'd had that same conversation before, as well as a similar situation when Malcolm and Jon were trying to disarm the warhead.)
Old enough to know better, but that's never stopped me before.