The worst thing about Trump's nomination may be that it makes Hillary unaccountable
But that isn't an option. In nominating Donald Trump, the Republican party is in the process of creating a situation in which there is no way a reasonable voter can hold Hillary responsible for anything she has ever done or said, or may do or say in the future.
Since no reasonable person could possibly vote for Trump, no reasonable person has any way of holding Hillary accountable for anything. And that may be the biggest problem with the Donald as Republican nominee: now,just as during the four years of the Clinton administration that Trump's nomination makes inevitable, there is simply no way to hold her accountable for anything.
Now, the alternative is unthinkable; then, the inevitable will be the reality.