They've never taken out a settlement the size of a city but there have been a couple of tailings dam collapses in recent years that have led to the deaths of (in one case) 270 people and (in the other) displacements of hundreds of people, along with widespread downstream pollution:

https://en.wikipedia.org/wiki/Brumadinho_dam_disaster

https://en.wikipedia.org/wiki/Mariana_dam_disaster

Then of course there's the drying up of the Aral Sea starting in the second half of the 20th century, due primarily to the diversion of the rivers that feed it for the purpose of irrigation, which has had a devastating effect on the surrounding communities that used to depend on it:

https://en.wikipedia.org/wiki/Aral_Sea

This reminds me of the theory that the Rapa Nui on Easter Island also suffered from self-inflicted "ecocide", cutting down all their trees to build their legendary Moai statues and ending up with no birds, unstable soil, erosion… all that comes with it.

This narrative resonates with a lot of people given our current climate crisis and can seem like an ominous warning, but it is also disputed.

Here's an article supporting this theory: https://writingscience.web.unc.edu/2017/09/the-ecocide-of-ea...

An one debunking it: https://theconversation.com/the-truth-about-easter-island-a-...

The loss of trees on Pacific islands seems like a decent example.

The toy examples of Polynesian islands get a lot of play here, although if you rule out the extremely marginal and isolated places like Henderson, Pitcairn and Easter islands, there's not much to go on.