Fifteen year olds do lots of stupid things and then grow up and wish they didn’t. Even though it’s irreversible (and can be very, very difficult for a spouse to hear), I can live with that knowledge, and give my spouse the support and encouragement to continue heading in the right direction. I would never hold it against them if they’ve truly done Tshuva.
Unless you’re talking about murder/rape/molestation which is a whole different story. Here, he did irreversible damage to SOMEONE ELSE. But as long as he did horrible things that only HE has to live with, I can be there to make living with it easier. That’s my job as a wife.