The Republicans in Congress -- majority leader Kevin McCarthy and Speaker Paul Ryan -- are already on record as being opposed to some of what Trump has threatened to do.
As President I don't think he will want to try and start boycotts of companies by posting messages in his twitter account. Again, he'll have to be careful what he says because there will be opportunities for legal action. Some of his fans seem to think he is this all-powerful being but I think Trump is going to discover that some of the head corporate honchos are pretty tough people too, probably a lot tougher (and smarter) than Trump is.
At least I hope so. I don't want to live in an America where if you do something the President doesn't like he goes on the Internet to flame or troll you.
The nightmare goes on!