What attacks could a president perform? An R congress will plant their heels. Even attempting to clean up malfeasance and nepotism at the SEC, "the President does not possess the power to fire the appointed Commissioners, a provision that was made to ensure the independence of the SEC."

https://en.wikipedia.org/wiki/U.S._Securities_and_Exchange_C...

He favours a "temporary" ban on nearly a quarter of the world's population entering the US, delays to company's ability to hire anyone from overseas and a trade war with China... and also talks a lot about attacking Wall Street though without appearing to have any concrete policies to deal with it.

I don't think an unfunded plan to cut corporation tax is really going to tip things in his favour.

Facing instability, financial markets tend to run the other way. Trump is instability personified.

Markets crave financial stability and Trump is impulsive and seems to either not understand, or not care, about the long-term effects of the policies he mentions.

One example is his plan to get Mexico to pay for his wall, which involves holding hostage the wire payments that flow from people in the U.S. to their relatives in Mexico.

Financial institutions make money on those payments, but from a broader perspective the concept of holding capital flows hostage to policy ideas is deeply scary to Wall Street.

What if Trump decides that capital from Middle East sovereign funds will be hindered until they pay a greater share of the cost of fighting ISIS? What if he decides to hinder capital flows from China until they let their currency's value rise more? Etc.

It's his own money (~$20 billion) he plays with these days. So he kept the entire gain.

No. That would be illegal manipulation, and he is not that dumb.