Trump is incompetent and personally unsuited for the office, but so far at least he hasn’t caused any disasters. He will likely get at least a few good things done over the next three years, so I see him more as a Jimmy Carter type, one who was a failed president but not a bottom of the list president like Buchanan, Andrew Johnson, or George W Bush.
Right now, he is just a freak show and if he doesn't pass anything, that is how he will remain. Especially if he loses the next set of elections.
If he manages to stick around and consolidate power, down ballot eventually he will make very bad decisions because Republicans would then be emboldened by they fact that they are "locked in" or at the very least, the bubble we are currently experiencing will burst and he will be seen the way Hoover or Bush were seen. He and his party will be blamed because it will be seen as years of unaccountable and bad government finally taking its toll.
This will be especially bad if he is in power long enough and there are very polarizing "Golden Grail" victories. I can see a court case at least allowing for states to make it impossible to perform legal abortions in their states (or make them outright illegal) being Trump's "Obamacare" or "Iraq" if Kennedy retires sooner rather than later. What kind of legacy does that set up?
So yeah, he either loses quickly, or at least gets reduced to a figure head the way all modern presidents eventually were or he keeps winning and is able to successful ram down very conservative policies that turn out to cause a large war, severe financial meltdown, or somehow casting law and government into so much disrepute that society just goes to sh**t and the former things end up happening anyways.