I'd give the edge to Leviathan Baam personally.
Dark Change Baam is strong. Well clear of the level of Corps Commanders. Had he fought White with killing intent, there's no doubt he'd have won easily (especially if he had decided to follow up on that attack that White barely blocked once). His eroding Shinsu is a plus that messes up with the Shinsu of the enemy over time. His stats are also impressive, despite Baam having never been a stat beast. He's got enough speed to keep up/outpace Prime White. His physical punches are strong enough to push him back through his guard, and his body is tough enough to withstand some basic slashes from him. He's incredibly solid overall.
However, I want to elaborate on Leviathan Baam. I feel like he isn't given enough credit. He was able to damage, push back a bit, and paralyze half of all-out real Dumas' body. Even if he wasn't on his level, he still proved to be an annoyance to him.
To put the magnitude of these feats into perspective, you have to think about how insanely strong Dumas is. In his armor form, before any transformation or Rosario Ignition, he was dominating Jinsung. Had Dumas gone for the kill, Jinsung would've taken lethal damage (potentially die) briefly after the match starting. Then, upon transforming for the first time and igniting Rosario, he instantly negged Jinsung, FT Yama, Karaka and Base Baam at once. Now, Jinsung and FT Yama weren't at their best, but regardless, these are really impressive feats.
Then we find out that armor Dumas can transform even more (pink form). Judging by the gap in performance against the BHs (his severely nerfed armless self went from being one-sidedly pushed back to easily slaughtering them), this form is a huge boost in power. It can't be compared whatsoever with the previous form.
Then you have the real Dumas. He's stated to be much stronger than his armor self. His body is simply on another level judging by how he can no-sell Baam's Twin Wings attack in Base (the same attack from a much weaker version of Baam nearly ripped off Kallavan's arm). When going all-out, Baam feels a form of reminiscence between him and a fucking FH. Before anyone jumps, no, I don't think Dumas is anywhere near a FH. Baam is simply reacting more strongly towards him because he can comprehend his power, unlike the fractions of the FHs/Urek/Zahard he has seen (that he can't scale yet). Still, one can't deny it's insane portrayal, which only adds up to his monstrous scaling by feats.
Levi Baam was able to injure, somewhat push back, paralyze part of the body, and overall annoy such a being. By de facto, I'd say this puts him immensely above CC Tier. Honestly, more so than Dark Change Baam IMO.
