During the first year of war in the east Soviet Union suffered 4 million casualties, which is actually third more than they had frontline troops at the start of the war. Germans had penetrated hundreds of kilometers into Soviet Union and conquered many large cities (though factories tended to evacuate before them).
All this seems like very extraordinary punishment for nation to take so quickly. It seems kinda surprising that Soviet Union didn't lose the war in the end.
Has there ever been state that endured comparable punishment only to bounce back and win the war?
The Second Punic War comes to mind. The Romans lost several major battles in quick succession, culminating in the battle of Cannae which was a disaster. Their first expedition to Spain also failed. Hannibal was free to roam the Italian peninsula, destroying towns loyal to Rome while securing alliances with cities like Capua which had defected to his side. The Roman Republic had to go to extreme lengths to rebuild their armies, including conscripting freed slaves and teenagers. Fortunately for them, enough of their Italian allies didn't defect and they had sufficiently large population that these early defeats were not as crippling as one might think.
Ultimately Rome was able to prevail. Hannibal lacked siege equipment and wasn't able to threaten the city of Rome itself. The Romans stopped trying to fight Hannibal directly and instead focused on denying him reinforcements. Their second invasion of Spain was much more successful. Eventually the Romans invaded Africa itself and defeated Hannibal at the battle of Zama, ending the war.