Lumiya vs Galen Marek

Depends what iteration Galen is in.

Lumiya.

Galen crushes her skull in with the force or wrecks her in sabers.

Lumiya ~ Lotf Luke

Galen stomps.

Galen will end her with the force before she even gets close

Lumiya

Lumiya has virtually zero relevant Force feats to put her in the same league as Galen, and due to her cybernetics, she's probably even more vulnerable to lightning than Vader is. 

I don't think Galen has ever seen anything like Lumiya's lightwhip, so that would give her a pretty big advantage in lightsaber combat. And considering Lumiya initially beat post-RotJ Luke, who was > or = RotJ Vader in sabers, who in turn is >>>TFU Vader, this should put Lumiya well above Galen as a duelist. 

I can see Lumiya seriously pressuring Galen in a duel, only to be wrecked horribly once Galen breaks out any of his Force powers.

IIRC, Luke believed Vader >> Lumiya in power. Even at his peak, I doubt Vader could completely dominate prime Galen.

Galen comfortably.

Galen gets overwhelmed quickly in a duel, but ragdolls outside that.

BreakofDawn wrote:IIRC, Luke believed Vader >> Lumiya in power. Even at his peak, I doubt Vader could completely dominate prime Galen.

Galen comfortably.

Oh, Vader is absolutely >>Lumiya in power. Galen is well above Lumiya in raw power, in skill, and in knowledge of the Force. Lumiya honestly has very, very little in the way of notable Force abilities beyond illusions, iirc. The only edge Lumiya has here is in dueling, due to her demonstrated superiority to post-RotJ Luke and her unorthodox weapon.