In the Transitional Program - written in 1938, before the USSR had clearly become a new imperialist centre - Trotsky felt able to write that, measured against the Nazis, Stalin's regime "does not differ, save in more unbridled savagery". In the same document, he refers to the fascist states as "totalitarian" - a term he elsewhere used frequently for Stalin's USSR after the mid-30s. And this while he still regarded the USSR as a "degenerated workers' state" (wrongly in our view).
The Stalinists in the USSR did create concentration camps, did murder millions and did ally with Hitler to invade other countries (and then did it happily by themselves later on!)
The GDR may not have been as "savage" as the Third Reich. I don't know enough to judge - but then Mussolini's Italy, at least until the 30s, was probably not as "savage" as Stalin's USSR by 1938. In any case, all these regimes, fascist and Stalinist, were "totalitarian" in that they prevented the emergence of any independent workers' organisations, even the most basic, and allowed absolutely no space for any democratic, let alone communist, dissent.
Isn't that clear?