Regrets begin as soon as the Soul leaves the body.
And there is no greater punishment than regretting in death.
1) How are the hypocrites punished in the depths of Jahannam?
2) Why is regret such a terrible punishment?
3) Why we must pity ourselves first?
4) Why to regret while alive is the greatest benefit, but regretting in death is futile and an 'azab?