He already has, his one trump card in any battle against any foe is his belief in the strength of his will. As a result he has usually come out on top, even against a fallen angel in his head.
A nice sentiment, but we are referring to the specific spiritual attack that Ferrovax, Mother Winter, Drakul, Vadderung, and the Lords of the Outer Night and the Red King use. I haven't seen any mortal being use such an ability or anything close to it. But Drakul makes me think Harry might just be able to.
In fairness to your idea, I suspect what Harry does internally if done externally to his foes would look rather similar to the Will Attack. I just don't think Dresden has levelled up enough.
I've always considered the will attack to be similar to reiatsu from Bleach. Basically if you can't breathe you shouldn't even be on the battlefield and it allows the true heavyweights to dominate an army of weaklings without expending a ton of energy.
So I think Harry will either develop some form of the will attack, if only to terrify a room full of sidhe or WC Vamps into submission.
Do they stories they tell of a persons will impact an entity? I'm just wondering that if no one knows Marcone, Thorned Namshiel, Bob, and the Spear of Freaking Destiny helped out against Ethniu and they think Dresden "solo'd a Titan" how will that impact Harry the Wizard of Chicago, the Winter Knight, and the 'Za Lord?
Interesting, hadn't thought about it like reiatsu but it certainly shares similarities. I can also see Harry using it to smash down stubborn White Council guys.
You raise a very interesting point. Generally, people seem to learn about what Dresden did in each book without him telling them. Butcher often doesn't explain it...it's sort of an implied word-of-mouth type thing. Definitely some beings/characters have remote viewing capabilities too. But IF no one knew how Harry had solo'd a Titan...that would certainly make some people even MORE nervous than they might be if they know how he did it.
I suspect though that the Merlin and other senior Wizards etc have enough knowledge to work it out. They know about Demonreach, and I suspect know about the Arma Christi (the artefacts of Christ), and they will know that he had to do a binding (that's a requirement for any being no matter the power). I would be interested to see what happens if Bob was reported. Mab would be interested in that, and so would the Senior Council and the older Wardens.
It will be interesting to see who amongst the supernatural nations/organisations will know how and what Harry did. Lara will know, Marcone, Nicodemus etc. But will the Librarians? The Venatori? The Svartalves? etc.