Many historical atrocities with death counts is a common one I'll run into.

You'll see "xy atrocity had caused the deaths of this many people*", where the additional note will say something like "The numbers reported in this study have been challenged by many scholars on the subject and has been accused of invalid methods".

It's super common with history around Communist countries, because for a lot of folks in the west, the black book of communism is taken as fact when it's far from it, and you have groups like the Victims of Communism memorial foundation that have huge coffers for pushing the black book line.