I think we had a really near miss just a few months ago with Donald Trump. He was as authoritarian as hitler in his early days in a similar position. Trump could still be the next Hitler when the next US elections come up again. What makes him the more dangerous is his access to nukes. IF he runs, and IF he gets in again, I believe he will be far more dangerous next time round, as his previous experience will no doubt be used to fire the military top brass who don't fall in behind him, and replace them with others who will. Add in what experience he's had with social media and it's ability to "condition" peoples minds - those two controlled together would allow any leader of that country to pretty much cancel the past and rewrite the future as he/she sees fit.
Likewise with whats happening throughout mainland Europe. There are now many to keep an eye on, plus a few hiding in the shadows yet to reveal themselves whilst they build up sufficient momentum and support to have a run at their elections.
Yeah, like Tom says, a very interesting and deep subject

Just think Emmanuel Macron