bad enough the worst, but one small mitigating factor is that he has no ideology or fixed beliefs. He is quite willing to completely reverse prior positions if it suits him. That works well enough for him when all that is at stake is words.
But he despises backing down in a fight. However ill-considered the fight may be. So here is the problem. If his various lieutenants, perhaps pursuing their own agendas--I'm looking at you, Jeff Sessions--get out in front of Trump, and commit the Trump administration to a given course of action, that will take Trump past the point of no return. It won't be a matter of backing down from words, it would be reversing policies and facts on the ground. He hates that.
So my point is, to the extent that Trump has been not quite worst-case since the election--not prosecuting Hillary, for example--that willingness to back away from the brink of madness may disappear, once the administration is actually in power and doing things.