So, first... why is she so powerful? She is the Devil of Domination, and it seems to focus on the sort of mental domination, and her character and goals revolve around a kind of authoritarian form of domination, control in a sort of dictator form. That's fine, but... is that really something people are more scared of than the possibility of a terrorist attack via explosives, the ever-present threat of being shot in an alleyway or something as primordial as the unknowable future or the very concept of the dark? I ...don't think so. And remember that Devils grow stronger the more people fear them. I can think of one easy way of making this work, and that's having her just be a liar. Have it be that Devils being fearful of Devils also power them up -this would explain why Chainsawman is so powerful, as being permanently erased from existence is something everyone can fear. But ...not Domination. It still wouldn't explain why she is so powerful, or so feared. In fact, being controlled by someone or something (like a government) else is actually something a fair few people like. More recent generations seem to lack direction in life and seem to want to be guided. It gives them an anchor, something reassuring, something to act where they feel unsure, something to choose when they doubt -hell, the main character is a perfect specimen of these sorts of people, going so far as to perfectly explain that exact mindset. Would she truly be so powerful when so many people would actually like her...?
Furthermore, her powers are easily beyond the scope of the concept of "Domination", going as far as killing people from a range by using random prisoners as ...proxy voodoo dolls(?), exploding Devils and Devilmen by pointing at them and apparently even resurrecting the dead (both humans and Devils/Devilmen). Furthermore, she can apparently use the Devils contracted by her slaves by proxy, even if they died? Wouldn't there be something in the contract that ends it upon death? Speaking of contracts, what the hell is that immortality contract she has set up? Some government man made a contract with her to give herself immortality...? What? Can you make a contract with a Devil to give them new powers? That kinda sounds like bullshit to me.
I liked her a lot when she was first introduced, she was enigmatic, cold, cunning and always in charge. I had assumed she was a human who had made a contract with something dealing with knowledge, perhaps a Devil related to the Future, or something revolving around paranoia birthed from being spied on -and that was how she always knew so much. When she is shown killing Snake Girl's goons using prisoners as some sort of medium for an attack, I changed my guess to "Fate". Lots of people are scared of the concept of being unable to change what will happen, and it would have been super cool if she had made her contract with Fate, allowing her to tamper with Fate, and perhaps see what it held in store before it came to be. Then we see her talking to the Master Devil Hunter, at which point I realized she was a Devil -due to her smiling upon him calling her a liar when she said she wanted to save more people (remember that all Devils hold some intrinsic sense of disdain towards humanity). Okay, well, then she's the incredibly powerful Devil herself! ...but then it ends up being Domination? Then why not make her be a puppet of the unseen Domination Devil, originally a Devil Hunter who had contracted with Domination (specific details could be worked out later, maybe she's a victim in the relationship, perhaps she actively wanted this, whatever)? It'd be funny, in a sense, considering the Puppet/Dark Devil's defeat at her hands, and here she was, a puppet being used as a fake body for the Devil.
I dunno, even still... I can't fully explain why I don't like her in these last few chapters. Apologies for the rant.