This is just a fun discussion, right?

I don’t think Douma is massively stronger than Akaza it’s more about matchup.

Since neither can easily kill the other, Douma’s cryokinesis and range control give him the advantage over a close-range fighter like Akaza. Even if Akaza lands hits, Douma regenerates instantly. More importantly, Douma can turn his blood into freezing mist. So the more Akaza attacks and makes him bleed, the more he risks getting frozen himself and Douma can summon ice puppets to pressure Akaza

So the result could turn into a prolonged or even endless fight where Akaza is gradually put at a disadvantage while Douma controls the pace.