The daughter's obviously an asshole for not contacting him all this time but honestly I'm leaning more towards him being the bigger asshole.

He offered to bail her step dad out and she refused. She could have said "sure thanks" but she didn't, meaning she genuinely wanted him there more than her step dad. She was a child when she cut him off and people do a lot of growing up in their 20s. It's not impossible she wants to reconcile and thought this would be a good way to do it. It's not like she's asking him for money, she's asking him to be in her wedding.

I do find it curious how he doesn't talk at all about why she cut him off in the first place. To me it seems kind of shocking that he said he regretted ever having her, seems like a pretty harsh thing to say about someone you raised for 15 years, whether you haven't seen her in a decade or not. Makes me wonder what their relationship was like when she was a kid. And what the cut off point was for him to declare himself "not her father" anymore. Year 5 of no contact? Year 7? Was it last year and she just missed the deadline?

Yes she's an asshole for not contacting him all that time, but it wouldn't be outrageous for him to step up and be the bigger person in this situation. Sure it must suck to feel like you were rejected, but he's reacting like he would do an ex who brushed him off when it's his own child who made the decision as a teenager. Lots of brides don't have their fathers to walk them down the isle, she probably has a lot of men in her life hat could do it, I think it's pretty cynical to assume she just wants you to make her wedding look good when the risk is losing your daughter for the rest of your lives.

Honestly for him it seems like this is about how he's seen how great his life his life is without a child and now he doesn't want to go back to having one.