I had the idea of turning the races against each other, recreating the mean 6 and send them to cause chaos before killing them, then the races would see it as an act of war. But how would you do it?

6974454
I would take notes from Palpatine. Give them a reason to divide and go to war against one another.

6974475
sounds right, and you make a clone army?

6974519
Doesn't necessarily have to be a clone army, but if you want to have your villain split everyone up to wage war on each other, you have to think like a villain, and examine everyone's weaknesses, then exploit them.