Ok hear me out ya all, let me cook. So we know that the concept of things can turn Into curses. I am not suggesting that Hitler had a ct and died therefore turning into curse spirit after dead I am talking about the negative energy surrounding Hitler as a figure so it's only natural him turning into a curse similar to mahito and being humanoid.

Ok so I thought of his ability while showering so bear with me

CT- hitler can create poisonous gass which is only ever effective inside enclosed place and overall he is as strong as mahito in the beginning and about as durable as megumi at his base

Domain expansion- now remember how I talked about him being comparable to mahito AT HIS BASE you see his domain expansion traps him and his opponent into a white void similar to Kinji Hakari but you see in his domain he becomes the best possible version of himself and his opponent because the worst version of himself that he has ever been (after recieving CT) so let's say yuji gets trapped in Hitler's domain well he becames as strong as he was in the beginning of the show after awakening his curse energy. Also Hitler will become the most powerful version of himself basically stacking things like getting a black flash or any kind of buff.

So yeah did I cook ?

Edit:

Also forgot to mention the effects of domain expansion lasts for the rest of the day for both sides even after it's closed.