[Warning, this will be a long post]
As Alakabamm stated above, Trinimac is certainly at least as powerful as Akatosh due to statements from the lore and possibly from defeating Lorkhan. Also, in case anyone was wondering, SpiralMaster perfectly summed up
here why Akatosh is placed at 2-A.
If Trinimac, is equal to Akatosh, then Malacath would would, by extension, be 2-A as well as opposed to 2-C due to being the same exact being as before, simply with a different mentality. However, as for Boethiah, I can really not say for certain whether or not she is warranted an upgrade as well. Skimming through the Imperial Library, I see conflicting stories either saying how she "defeated" Trinimac and then consumed him, or how she simply "corrupted" him and ruined his image to his followers. In other words, it is too vague to place Boethiah at 2-A in my honest opinion.
This however, does bring up some of the other Princes as well. Jyggalag, for example, is stated as being one the strongest Daedric princes. This would logically include all of the other Daedric Princes, including Malacath. Henceforth, Jyggalag would be given a 2-A ranking as well.
This may seem odd, but not as much as one might think.
[History lesson inbound] The Aedra and Daedra are also known as the Et'Ada, who were the old spirits born of Anu and Padomay's interplay. The Aedra (who were not called Aedra yet at this point) were born of the mixing between the Blood of Anu and Padomay, whereas the Daedra were born strictly of Padomay's blood, and are thus, completely alien beings of different nature to man. Akatosh, being the first Et'Ada to form is also one of the most powerful as we have seen.
[History lesson over] The reason I brought this up is because it shows that Akatosh is one of the most powerful of the Aedra, whereas the Daedra are a completely separate group of beings, and it stands to reason, that they would most likely have their own beings that stand at the top of the power ladder (Like Jyggalag). By this, it would not be impractical to assume that Jyggalag is likely 2-A as well due to being a threat to the other Princes, and that his domain
"extends accross the sea of Oblivion" (under the Jyggalag section).
Now, this also begs the question, would Sheogorath be higher than 2-C? I would honestly think so, and here's why. If Trinimac was simply
tricked and corrupted by Boethiah, and never technically beaten in combat by her, then Boethiah is not warranted an upgrade. However, it does mean that Malacath is still 2-A due to still being the same god, just with a twisted persona (as I stated above previously). By this same logic, Sheogorath would be no weaker than Jyggalag, just simply the same being with a completely different visage. This is the exact same instance with Boethiah, because there are conflictions on whether or not Jyggalag was "defeated" by all of the other Princes, or simply
cursed to live as what he hated most out of hatred and fear from the others (Noted under the "Jyggalag" section).
So what this tells us is that we have 2 options: First being that we go with the idea that Boethiah "beat" Trinimac, and that the other princes "beat" Jyggalag and upgrade them all to some degree. Though this option would make less sense as it would imply that Boethiah and, by extension, all of the other princes are on Akatosh's level, which is absurd. OR, we go with the prospect that Malacath and Sheograth were manipulated in a different way, but still posses the same power that they did previously (as nothing implies that they ever were weakend by their transformations). This option would make much more sense imo.
Anyway, that's my very long 2 cents. Feel free to ask any questions or tell me if you disagree with something or if I made a mistake.
