I don't think Cyn was ever in the wrong throughout the entire show and every act they partook in was entirely justified.

Starting off with the most heinous allegations, mass genocide and destruction of the planet. Personally, I feel as if it's a bit disingenuous to pin the blame on Cyn for earth's destruction and the extinction of humanity. Take a look at our real world, constant wars, destruction, and climate change all caused solely by humanity. Humans were gonna kill themselves anyways. Cyn was just ending it early and preventing additional years of suffering and torment caused by changes in the earth (changes caused by humanity, might I add).

Another similar allegation was another count of attempted genocide and destruction of another planet, this time it being copper-9 and the worker drones rather than earth and humans. The claim of another count of genocide is verifiably incorrect. The genocide of worker drones was carried out by N, V, and J. Not Cyn.   
  
"But they were working with Cyn". So what? How do we know that Cyn told them specifically to kill worker drones? They killed worker drones to stop their systems from heating up, but how do we know that this "heating up" thing was caused by Cyn? They could've done it themselves. Another thing I want to note: notice how the moment Cyn shows up on Copper-9 the mindless killing of worker drones mostly stops?   
curious.

As for the destruction of Copper-9, that fixed itself within a day, so no harm no foul.

Another allegation is about her wearing Tessa's skin. This is true, although people do often leave out crucial information. Tessa was a grave robber who stole the hair off corpses for her robots. This is a blatant immoral thing to do, disrespecting the dead. It's only justice that Tessa befalls a similar fate.

Now there are some other things such as erasing N's memories, being a jerk to Uzi, and also probably torture, but that's also all defendable.

"Innocent until proven guilty in a court of law" is a very important rule to live by. Assuming the worst of people can lead to innocent people facing consequences for another's actions. Cyn has never been sent to court, much less proven guilty for anything.  
Therefore: she did nothing wrong.

TLDR: the only thing cyn is guilt of is being a silly lil guy

Cyn didn't do anything wrong.