As even a type 1 civilization it costs you almost nothing to send a big ball of death a few million years into the future to wipe out a possible future rival.

The timescales are where things get tricky. If you wait for them to become a problem they will be a problem for millennia. and that problem will metastasize.

Now if you have FTL figured out. I mean. Carl from accounting could wipe out all life on earth because he had a bad day.