Harry is out of the White Council and already has control of a significant group of talented people -- the Paranet. While they are, by and large, not wizard level talents -- they have Elaine.
Elaine is pretty close to pre-Winter Knight Harry. She was smoother, he had more muscle.
If you think about it, the White Council has very few people who could (or would be willing to) take on Harry. Listens to Wind and McCoy are damaged, or won't. Good luck with the Treason charge Merlin.... Rashid can't be risked given the state of the Gates, and its not clear he would.
The Merlin of course could, but that would be a terrible risk and as good as a declaration of War against Winter. Christos? Liberty? Mai? Christos can throw down, but is he man enough to do so? Liberty and Mai don't seem like fighters.
Chandler, Yoki, Wild Bill and Ramirez might have working together. But, Yoki and Bill are done. Chandler is in the shadow realm and Ramirez is not up to it. Maybe they've got some of the older wardens too, but those people were frightened of pre-Winter Knight Harry. They probably wet their beds thinking about post-Winter Knight Harry Dresden with access to the Eye and a legion of chained horrors begging for parole.
Captain Lucio? I don't know that she would thrown down with Harry, but would the White Council risk that given her past relationship with Harry? Besides, she's still not as good as she had been pre-corpse taker.
In the end, after fifteen years of war, most of their most powerful assets from a direct confrontational point of view are depleted, damaged or have questionable loyalties where Harry is involved.
This was a stupid bluff by the Merlin.