"A word that means wicked and also the highest degree or most extreme form of something"
Solution 1:
I doubt that you will find an official term; as you noted, petty treason and high treason are degrees based on the entity that was betrayed. It is unlikely that the English language will have settled on a single term for treason that is greater than high treason (treason against a sovereign), because such a term would not historically have been necessary.
With that said, for your science fiction example, you should feel free to use creative license in developing a term. I would suggest using a synonym of utmost, such as:
- extreme treason
- highest treason
- peak treason
- ultimate treason
- utmost/uttermost treason
- zenithal treason
...and so forth.
Solution 2:
Consider,
supreme treason.
supreme
: highest in degree or quality : greatest or highest possible M-W
the most ignominious treason
ignominious
1 : marked with or characterized by disgrace or shame : dishonorable
2 : deserving of shame or infamy : despicable M-W
the most infamous treason
infamous
1 : having a reputation of the worst kind : notoriously evil
2 : causing or bringing infamy : disgraceful
3 : convicted of an offense bringing infamy M-W
People, a horrible treason, an infamous treason threatens our independence, our adored independence, for which our fathers gave their lives! Eagles and Empire