So according to HK-47 the Sith generally don’t feel Fear.
In the Darth Vader Comics Darth Vader makes it clear that he abandons Fear for Anger & Hate with Sidious making it clear that Suffering is the final step.
In otherwords the Sith’s weakness is falling to Anger, Hatred and Pain while ignoring Fear.
Fear contains(as per Yin and Yang) the White Flare(as Star Wars Visions calls it) and Black Current(also as Star Wars Visions calls it) of the Force and is infact the Speck of Darkness within the White Flare of the Dark Side just as Compassion is the Speck of Light within the Black Current of the Light Side.
The Sith mostly ignore the Core of their Darkness in favor of the Light surrounding it while the Jedi mostly ignore the Core of their Light in favor of the Darkness surrounding it. Ironic isn’t it?
The Jedi at the least had Fear to balance out the lack of Compassion whether they knew it or not so they had a Core of Light to give them Balance while the Sith had mostly Light with barely any Core of Darkness.
The Light of Wrath, Passion, Hatred and Pain flooded the Sith purging them of Fear making them into a Cancer in the Force.
Incidentally the Sith Emperor being an Avatar of the Black Current is filled with Apathy & Fear with spikes of Anger and thus is more balanced than the other Sith which allowed him to notice the imbalance in his Sith Empire. His children fell to the same imbalance as the Sith did which led to their downfall.
Vowrawn seems to lack Anger and thus is imbalanced in the opposite manner from the Sith being completely apathetic and thus a true embodiment of the Black Current.
Acina has some Anger but not enough of it to Balance out the Black Current emanating from her so she has the same Imbalance as Vowrawn.
If any proper Sith Saga were to be made where Anakin’s Force Ghost destroys the last remnants of the Sith as per the Chosen One Prophecy were to be made Vowrawn and Acina would be the Final Villains representing the final Cancer in the Force representing the Sith.
The First Sith Emperor while not an Imbalance would be a threat to the Galaxy needing all the great heroes(including possibly Traya who would preferably be a Night Sister in Canon) working together to defeat him but Vowrawn and Acina would be a threat to the Force’s own Balance and thus need to be taken out by Anakin’s Force Ghost at the end of the Sith Saga.
The possibility of the Sith still existing despite Sidious/Bane’s defeat(and yes Sidious is clearly Darth Bane considering he makes it clear that he is all the Sith and that killing him in Anger or Hatred results in him possessing the killer) is implied by the Canon Aftermath Novels that state that a Dark Side Wellspring distinct from Exegol was calling to Sidious from the Unknown Regions.
So for a Sith Saga would you want the Villains to be Vitiate, Acina, Vowrawn, Grand Admiral Thrawn, Zorba the Hutt and Supreme Prophet Kadann(with a Starry Robe and Gul’dan-like Face complete with Glowing Red Eyes but with Human Skin Color) with hints to the 5 Gods of Iokath lurking beyond the horizon?
Would you want the Heroes of the Sith Saga to be Ashoka, Yaddle, Oppo Rancisis, Force Ghost Yoda, Force Ghost Anakin, Darth Traya(who would be a Night Sister instead of a Sith in Canon), G0-T0, Chewbacca, HK-47, R2-D2(who would turn out to be Darth Nihilus who would be a Night Brother instead of a Sith in Canon) and C3PO?
INB4 someone tells me I should have added Rey(✲shudders✲) or some completely new Protagonist to the above list.