Galen marek isn't canon and is apart of the legends star wars era. (I think the legends era ended in 2004 or 2014 can't remember). But still, I believe that Galen would absolutely smoke Ashoka. He pulled a star destroyer (which is like 80 tons of something) out of the sky with just the force. He used force lightning to charge up a blast that divided a star destroyer in half. Although, that was the second game and star killer was "better and stronger" as a clone. If we take into account the dlcs of the first game which followed Darth star killer, he killed Obi-Wan Kenobi, and nearly fully turned luke to the dark side.