No, I can’t promise that Trump, if elected, or anyone else if elected, would not become a fascist dictator.
It’s the Constitution that makes that promise.
Sadly, Trump has already indicated he is on board with the idea of using unconstitutional executive actions a la Obama to bypass Congress if needed - but HE would use that power for GOOD. And many Trump supporters here on this forum have supported that idea, claiming that to save the Constitution, we need to have a president who will ignore the Constitution the way Obama has... So relying on the Constitution to keep a President Trump in check may not be effective.