Zelda II The Adventure of Link
I do not like this game.
I know it has it's fans and I know it's technically a main Zelda game... but it's just not. It doesn't feel like a Zelda game should. This is mostly a side-scrolling beat-em-up with Zelda trappings. It doesn't have the freedom and open exploration of the original and it definitely doesn't feel like any other Zelda game out there.
I wish I liked this game enough to actually finish it once. But, I don't. This is one of the few Zelda games that I've never finished. At this point I've come to the realization that I never will and I'm ok with that.
So please forgive how much I'm glossing over this one. If you're a fan of it let me know. I'd love to hear from the perspective of someone who really likes this game.
But there's no question in my mind that this is the odd one out for the Zelda series.