"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