Subject: Re: "Totally innocent" Trump
Not quite to the level of dictatorial powers, but with no oversight (due to immunity), the Executive could do all sorts of criminal things, and get away with it because no one could access the evidence. Hence, Sotomayor's concern about using assassins for political enemies with impunity.

Again, this seems incredibly unlikely. The President would be immune, but no one else would be. Even if the President might be immune for ordering the FBI director to murder a political rival, the FBI director would not be immune for agreeing to murder the political rival.