"I remember in my childhood, when we argued in the courtyard, we used to say: it takes one to know one. That’s not … just a children’s saying or joke."

"We always see our own traits in other people and think they are like how we really are. And as a result we assess [a person’s] activities and give assessments."

Said Vladimir Putin, quoted in "'Takes one to know one': Putin-Biden spat escalates after 'killer' accusation/Officials in Moscow go on offensive after Biden says Russian president will pay price for election meddling" (The Guardian).

Putin added, ominously: "I would tell him: Be healthy. I wish him good health. I say this without irony, without joking."

"North Korea: Kim Jong-un's sister warns US not to 'cause a stink.'"

BBC reports.

Kim Yo-jong was quoted in the official Rodong Sinmun newspaper as saying: "A word of advice to the new administration of the United States that is struggling to spread the smell of gunpowder on our land from across the ocean. "If it wants to sleep in peace for [the] coming four years, it had better refrain from causing a stink at its first step."...

Also:

Pyongyang has yet to acknowledge that President Biden is now in office.... 

Relations between the US and North Korea plummeted in 2017, when the North tested long-range missiles capable of hitting American cities. Tensions eased as President Donald Trump sought to develop a personal rapport with Mr Kim....

Biden has yet to announce his policy on North Korea, but during his campaign, he called Kim a "thug."