Not just the ending so much as the ending and the last few hours leading to it, but Xenoblade Chronicles.
The interesting villain dies to be replaced by the most boring villain ever who just repeats himself endlessly rather than have a personality, and the interesting world you're in is revealed to be an accident an incompetent scientist brought about, making it feel dumb and mundane instead of cool and unique. And the very end reveals absolutely nothing about anything, you find out that people survived and...yep, that's it. What changed in the world, how the different people are going to co-exist, why Melia is even a character that exists when her whole arc goes nowhere, none of it is covered because the ending is just some generic "stuff happened" scene building up to a big reveal that you were already told about five times before the ending even happened anyway.
I've never played a game that fell apart worse in its final stretch than this one. ---
We clasped our hands, our hands in praise of a conquerors right to tyranny