Nazi (national-socialist) Germany was totally socialist.
P.S. Your description of „socialism“ is a veeeery weird one. Apparently everything is socialist.
There are no Marxist regimes; all “Communist” regimes are (or are derived from) Leninism which introduces vanguardism and other changes to avoid the prerequisite of developing proletarian class consciousness through mature capitalism in Marxism, and feature a (theoretically) transitional initial phase to replace development through private capitalism, which none have ever escaped from to anything that was supposed to be beyond it (though China rewrote the plan to include authoritarian quasi-private capitalism.)
There's a wide array of arguably socialist non-“Communist” regimes, but all of them are democratic/market socialism that explicitly accepts plural democracy and regulated (not “free”) markets as important elements.
> Nazi (national-socialist) Germany was totally socialist.
This is true to about the same extent as “the Democratic People's Republic of Korea is totally a democratic republic” is true.
I don't know, it seems like a lot of European countries with a pluralistic party system are heavily "Christian Socialist" (pro free market, pro property ownership, pro capitalist, pro safety net) and they don't seem to be any more prone to slide into dictatorship?
I've actually have never read a compiled lists of stats of what types of government make a country impervious to dictatorial rule.