I interpreted GP as talking specifically about induced regime collapse, specifically one induced externally. As in, not about the regime itself slowly decaying into a more benign form, but rather about attempts to remove it by force.
Historically, I can't think of a single case of a regime being destroyed through revolution or invasion that didn't end in at least partial societal collapse and a drastic increase in deaths and suffering for a generation or more.
The Nazi Reich? Arguably it brought about its own downfall via its misguided attempts at "invasion" - at any rate it was about as violent and sudden an end to a regime as you could ask for. But history is full of coups d'etat that didn't necessarily negatively impact the greater population all that directly.
You're right, Nazi Reich is a valid counterexample to my assertion. It was destroyed by external forces, though as you say it was totally self-inflicted, and a lot of people living under it suffered greatly in the process, but the situation for them improved very quickly.
Per my understanding of history, that last part was an anomaly in several ways. This being a world war is one way, of course, but another factor was that the hot war between the Allies and the Axis transformed, after the Axis was defeated, into a cold war between members of the Allies. Both sides of this new conflict considered it critical to capture and stabilize the very territories they helped liberate from the Nazis. This wasn't a half-hearted "nation-building" program like we've been seeing in more recent times - both the US and USSR committed tremendous amounts of resources to get Europe back into shape, because this was still a war - arguably the same war, just going through a cool-down period - and both sides expected it to go hot eventually.
Also, while Germany survived the death of Nazi regime quite well, the Cold War is also known for US and USSR sponsoring and orchestrating coups and regime changes all around the world, and (AFAIK) those cases all ended badly for the locals.
In some sense, it might be that World War II was itself an anomaly - I can't think of any other war that ended with both the winners and the losers coming out better off. But it's also worth remembering that WWII itself was in large part a consequence of the societal collapse Germany underwent after losing WWI. And the subsequent Cold War was in large part a consequence of societal collapse caused by bloody revolutions in Russia and elsewhere around the start of the 20th century.
The way I see it, we have one special case of regime collapse making everyone better off almost immediately, but even that one is surrounded and infused with countless cases of regime changes that caused generations to suffer.
I asked ChatGPT for some other examples - it listed "the overthrow of the Somoza dictatorship in Nicaragua in 1979 [by] the Sandinista National Liberation Front" and "the overthrow of the Marcos dictatorship in the Philippines in 1986".
With additional prompting it also listed the overthrow of the apartheid regime in South Africa, and the Solidarity movement's ultimate success in Poland in 1989.
Historically, I can't think of a single case of a regime being destroyed through revolution or invasion that didn't end in at least partial societal collapse and a drastic increase in deaths and suffering for a generation or more.