There are a bajillion crappy old games that I actually dislike more, but none of those would be interesting answers.
Of games that are generally well-regarded, so the gap between my opinion and the common opinion is largest, I’d have to say Final Fantasy Tactics.
It’s not that I dislike it - it’s just that, between FFT and Tactics Ogre, there are five games of the same type from the same devs and the same general era (FFT, FFT Advance, FFT A2, Tactics Ogre: Let Us Cling Together and Tactics Ogre: Knight of Lodis) and IMO, FFT is the bottom of the barrel - every single one of the others is better.