Sure, there was the attempted assassination of Reagan and the fears for Obama as the first black President, but in those cases it was a lone nutter rather than a conspiracy.
How long can Trump crash the market before an angry billionaire decides to take him out? The remaining Koch brother is already pouring money into legal challenges against Trump…
Hitler, unlike Trump, fought in an actual war. If nothing else, that goes a long way towards respecting the power of violence - both to give and receive it.