We know that Zhu Yan being rumoured to be the most evil is both true and false, he's not personally evil but when he's controlled by the malicious chi he kills people. This difference probably doesn't matter if he's slaughtered your whole family. But there is another rumour:
[Everyone knows that when Zhu Yan appears, chaos will erupt]
In Ep 5 we learn the origin of this rumour, it's because he's a cop! The chaos isn't caused by him, he's following it. The second Ran Yi sees Zhu Yan he assumes it's to take him out of the human world:
Zhu Yan is being blamed for cleaning up demon messes and sending them back to the Wilderness.











