The Scarlet Letter centers around one sin, adultery. Most of the other sins in the novelradiate from that one. I assume from your question that you're referring to adultery as the "initial sin." The three characters you mention each respond differently to this sin/crime of adultery.
Hester is relatively unmoved by it, despite the fact that she suffers the most public shame. It's clear as the story progresses that Hester had no regrets about her actions; in fact, we know she would do it all over again, as she was willing to leave with Arthur and live as an unmarried couple. Hester is unrepentant of her sin. Arthur, on the other hand, is consumed with guilt over his actions. He clearly loved Hester once, as he's not the type of man who would sin in such a way if he were not moved by a great passion. He has trouble living with himself after they have been found out (okay, after Hester has been found out) and regularly abuses his body in the unfulfilled hope of purging his soul of guilt. He does appear to have repented and made peace with God before he dies. Roger Chillingworth is the wronged party in this sin, and his initial reaction is unexpectedly mild. He understands his marriage to Hester was not based on love, and he seems willing to forgive Hester based on the small comfort he found with her before she left for America. The revelation is the beginning, though, of a deadly descent into bitterness and revenge for Chillingworth. Once he is thwarted in his quest for revenge he has no reason to live.