Correct
一失足成千古恨
/ yī shīzú chéng qiāngǔ hèn /
Strokes
Definition
a single slip may cause everlasting sorrow (idiom)
Example
Definition
the error of a moment becomes the remorse of a lifetime; one false step brings about eternal regret; a single slip may cause lasting sorrow; one false step involves one in endless ruin