Cal Cestis vs. The Grand Inquisitor

Force sabers all out

Grand Inquisitor takes sabers, Cal takes Force. Even split, leaning Cal

GI.

grand inquisitor takes sabers,cal force all out cal 6/10 times

GI in sabers, Cal in Force. It was confirmed by Filoni that the GI >> season 1 Kanan because Kanan doubted his abilities and connection to the Force, and in doing so ultimately hindered himself.

GI in sabers. I'm hesitant to say Cal actually takes Force. Cal's Force use in cutscenes is pretty light, and most gameplay aspects aren't necessarily canon. In a moment of desperation, he stunned a handful of clones. He Force pushed Masana Tide after he'd already sliced off her hand and scored a deep cut in her back. And he threw a piece of machinery at Vader. Those are his best Force feats that I recall.

The Grand Inquisitor hasn't really been depicted using the Force against non-Force sensitives, but he consistently ragdolled S1 Kanan in every single duel. Kanan, even as of S1, is no slouch when it comes to Force use. I'd argue he's easily comparable to Cal, so the GI's ability to consistently ragdoll Kanan should mean he's got an edge over Cal as well.

It'd be a really close fight, and I'd love to see these two square off in a potential sequel, but I'd say the Grand Inquisitor should have the overall edge.

The Ninth Sister is also a pretty crap combatant.