A notable example is the way that gun violence data has been continuously and specifically suppressed by those who oppose gun control in the US (e.g: the Dickey Amendment, which had an extreme chilling effect on the CDC studying gun violence).

Unfortunately, it is common for those with power to see the data as a stick they can be beaten with rather than as a tool to do better.

Of course, an example of the negative potential also comes to mind: recently we got proof of extreme gerrymandering done using racial data. Obviously that isn't to suggest that data shouldn't exist, but more to underline your last point: fundamentally it can only be beneficial if people come to it in good faith.