“The victors write the history books” is a well-known observation, and it seems to be borne out by our (Western) views of history: We consider e.g. the Persian invasion of Greece, the Arab and Mongol invasions of Europe, the French ancien régime, the colonialization of America, Africa and most of Asia by European powers, the Ottoman empire, Franco’s coup, Nazism, Soviet hegemony over Eastern Europe all in an unfavourable light, and they were all ultimately defeated/reversed, even if they temporarily (in some cases: for centuries) had the upper hand.
Possible counterexamples that I can think of are the Chinese invasion of Tibet and the Armenian genocide, but these are arguably not history yet but unresolved political issues, as uncoerced historical discussion is not yet possible in China and Turkey, respectively.
So, are there cases where there is a consensus among historians and the historically interested international public that in the conflict between A and B, B was in the right, even if A won, and won for good? To qualify this consensus should include the political/enthnic descendants/successors of A, if any.