So, to begin with, I think they already did the same major things he did last time, that is: reversing Biden orders, killing treaties and trade agreements, reducing military support, threatening allies, and borrowing around $4T.
Beyond that, they are experimenting with what they can get away with.
This includes:
Everything Doge, including mass layoffs, USAID, DOE
Ending birthright citizenship.
Controlling universities
Aggressively controlling press access
Redefining immigrants, protestors, gangs, terrorists, and wars so they are all the same thing.
Using that to remove due process and torture them in El Salvador
All unconstitutional, in some cases blatantly.
But will the SCOTUS say no?
If the SCOTUS says no, can he do it anyway since he controls the DOJ, FBI, etc.?
How long will it take anyone to stop him anyway?
In other words is there a chink in the armor of the Republic?
If he is completely stopped here-- then I think he will slow down. But if there is a vulnerability then I expect he will double down on those wins. If he gets away with ignoring one law, he will try ignoring the next law. If he gets away with locking up a protester, he will lock up all the protesters. Etc.
I also expect at least some more experimentation. I don’t know what might be. If I had to throw a guess, I think he might start a war, use a catastrophe, or simply provoke massive protests in order to excuse martial law, which will in turn be used to suspend the next election. But hopefully he he will get sick and die before then, and won’t have a willing/able heir to follow through.