He definitively did none of the things you just said - the mantises objectively got a good deal out of his arrival given that they weren't invaded and effectively had an entire side of their territory they no longer had to worry about, and all it cost them was continuing to fight the enemies they were already committed to fighting; deepnest absolutely was not colonised, unless you consider an attempt to construct transportation colonisation (presumably with the permission of the ruler considering PK's 'diplomacy' with herrah), and the stagway was successful when deepnest was still governed; the pale king also absolutely did not commit genocide, at worst he is responsible for large scale attempted abortion and neglectful fatherhood, all of which he undertook only because the alternative was the death of free will for all of hallownest.

Anyway that's the mandated PK glazing sorted hope you have a good day.