Eliphaz false analysis carries a false remedy. He was in fact entirely wrong as God’s intervention at the end of the book shows.
Obviously repentance is the right course of action for someone who has really turned to away from God, and it would be right to encourage repentance in such a case. True reformation, as David Thomas says, involves several steps. It involves a heartfelt return to God that cleanses the soul from all duplicity so that the returning sinner is no longer playing games with the Lord and trying to have God’s smile and keep his sin at the same time. It therefore also involves the fruit that follows from repentance: turning away from all known deceit and lust, making retribution where possible, and taking up the fight against our sinful nature within. Iniquty is removed far from our tents; our hatred for it makes us more resolved to resist the devil. The Christian must make no provision for the flesh and give no foothold to the devil in bringing him down.