There's no one more active than Germans themselves.
We don't blame just one nation for the Holocaust, we blame everyone. The Americans could have bombed the railroad to Auchwitz and save more tens of thousands of Jews, they know about it, but they didn't do it.
Soviets (Ukranians and Russians) didn't let Jewish refugees into the USSR, invaded Poland together with Germany in 1939, had no plan to fight with Germany until operation Barbarossa in 1941.
Yet obviously the Germans are the worst.
Jews were persecuted long before WW2. In the USSR, Jews were hunted in Pogroms.
We were thrown to the side by every nation.