Yeah. As others have complained, she doesn't do a good job of being a threat. Part of the problem to me seems to be the Author deciding to flesh out and add breadth to the story when making the LN, but did not really change the main points & event flow of the WN. Therefore, the characters added don't effect things ultimately, and are practically filler. For her buildup, she really should've intruded more into the upcoming Empire parts and had that turn into a big thing, instead of her turning into an afterthought and a Rimaru flex.
Look, all I'm saying, Mariabel, you could totally turn over a new leaf like Clayman in his spin-off!
He's pretty happy! Wouldn't that be nice? No? Well, I tried.
You really can't fix her. Even in her previous life, engineering wars between countries for fun was her pastime. At this point, she's just a lost cause.