rock bottom; the very bottom
Used both literally for the lowest physical point and figuratively for the worst state in life, mood, or economy.
失業して、気持ちがどん底まで落ち込んだ。
After losing my job, my spirits hit rock bottom.
景気はどん底から少しずつ回復している。
The economy is gradually recovering from rock bottom.
He was in the depths of despair.
The company went bankrupt, and our life fell to rock bottom.
He climbed up from rock bottom and achieved success.
After the war, many people experienced life at rock bottom.