North Korean dictator Kim Jong Un’s sister could be the Hermit Kingdom’s most brutal leader if she succeeds him, experts told The Post on Monday. Kim Yo Jong, 32, appeared poised to take the reins of power amid a claim that her older brother has been in a coma for months and his recent public appearances have been staged. “I haven’t seen any evidence, any indication of how she might rule, but my speculation — given the reputation and history of the family — is that she would rule with an iron fist,” retired US Army Col. David Maxwell said.