I've been running through Voyager episodes for the first time since it originally aired, and out of every episode in the series (Except for the three I skipped, Threshold and the two Fair Haven eps), two stand out as by far the worst.
1. False Profit. It almost made me want to quit watching. And then I realized, when it originally aired, it made me quit Voyager for a couple weeks before coming back to it a little later in the season. If any episode makes you almost quit the entire series, twice, I think it's by far the worst episode.
2. Inside Man. Holy crap, what a bad episode. Besides the fact that it brings the farengi back to the cartoonish level of ridiculous evil they were in season one of Next Generation, it makes no sense. Durr durr I'm Janeway, I'm going to take the ship into this phenomenon that to my knowledge is a death sentence, and take it on faith that these shield improvements and inoculations work without thoroughly testing it.
After DS9 turned the farengi from something cartoonish and silly into something a little more gray and far more interesting, Voyager brings them back to the abject silliness and absurd capitalist caricature they were originally meant to be. What the heck were the writers thinking?