Whose sins you shall forgive, they are forgiven them; and whose sins you shall retain, they are retained.
[John 20:23]
God.
i John 1:9If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.
He promised that if I confess, HE would forgive and cleanse.
I believe Him. Don't you?
FWIW, even supposing Catholic's claims are true, there are no apostles left alive to retain or remit sin.