Gunbreaker vs. Dark Knight

[Absimiliard]

If the Gunbreaker had committed some injustice and used their position and abilities to escape punishment, the Dark Knight will win.

If the Dark Knight is attempting to intrude upon something or someone the Gunbreaker has sworn to protect, the Gunbreaker will win.

This isn't actually facetious: I strongly suspect that the motivations of the combatants matter a great deal. Especially for the Dark Knight, who is basically powered by their strong emotions, and from what we see in the questlines, become more powerful when they have something to truly fight for.

And what if neither of them have strong motivation? Or, for that matter, their motivations are equal. I.e. the Gunbreaker is protecting someone important to them that happens to have taken the life of someone close to the Dark Knight. The Gunbreaker has their charge, the Dark Knight has a deep wellspring of rage and grief from which to draw power.

DRK dunks on GUN as soon as he gets enough bloody aether stored up to start the 2v1 with his shadow buddy

The gauge is just a game mechanic. I would be extremely surprised to find out they need to spend anywhere near that much time building aether in lore.