I've been disappointed by a few that I've owned.
Spector Rebop: Love the look, love the feel and playability, hate the tone. I could occasionally dial in a good tone with a healthy amount of tweaking, but if I made any slight changes it was lost.
Warwick Corvette Standard Ash: I love Warwicks. I've had several, played several more. I absolutely hated this bass. It was a 2009 model I believe, and had the new thinner profile neck. I couldn't stand playing it. I much prefer the thicker, chunkier necks by far. And the tone, it was dull and lifeless. It was passive. While it was definitely punchy, after that initial punch it just sounded flat and didn't go anywhere. Couldn't wait to get rid of that (have since replaced it with a Corvette standard bubinga active, and I don't think I'll ever give it up. I love it!)
G&L L-2500 Tribute: Another bass which looks great and felt great, but the tone simply did not do it for me at all. Some people love it, and that's great, but again I found it too difficult to dial in the tones I liked, and even when I did, I only liked them at best. Never loved them. I just traded that a few days ago, looking forward to its replacement (P-bass ftw!)