Sounds like you need to move on. Leaving on a good note is something you'll never regret. I've done it both ways, and I recommend not trying to settle scores on the way out. Some employers give what they call an "exit interview." They encourage you to tell them anything negative you have to say. Don't take the bait. Stick with the "bad fit" story. Thank them for giving you the opportunity to have worked there. Maintaining your composure in that way can actually feel self-empowering.