The very bottom; rock bottom — the lowest point, literal or figurative (e.g., someone's life or luck).
会社の倒産で彼は人生などん底に落ちた。
When his company went bankrupt, he hit rock bottom in life.
失恋して彼は精神的などん底にいた。
After the breakup he was in an emotional rock bottom.
景気は今、どん底だと言われている。
They say the economy is at rock bottom right now.