Alright, if the Shades can only be defeated by Salmon, that begs the question: how do the UNA win in Salmon's dark future? With Salmon removed from the timeline, the Shades should not have been defeated.

There are a few solutions to this:
a) The Shades can be beat without Salmon
b) The dark future is one in which the Shades win.
c) Time in Avbaroy is a stable time loop. Salmon goes back in time, defeats the Shades but fails to defeat the UNA, creating the dark future.

Problems with the solutions...
a) Already contradicted by word of God from Threeshades
b) Contradicted by the fact that Salmon saw Ins in the future. It is unlikely that Threeshades would have allowed him to live.
c) FI truly becomes hopeless, as the future is unchangeable and Avbaroy is doomed to UNA rule.