1 to regret

2 to repent

1 to renege

2 to go back (on a deal)

3 to back out (of a promise)

1 too late for regrets (idiom); It is useless to repent after the event.

1 to regret

1 remorse

2 repentance

1 too late for regrets (idiom); It is useless to repent after the event.

1 to regret one's past deeds (idiom)

1 too late for regrets (idiom); It is useless to repent after the event.

1 to feel remorse and shame (idiom)

1 to repent and start afresh (idiom); to turn over a new leaf