I've always felt the best "confrontation" is to have them served with divorce papers along with some of the evidence if possible. Then just go dark.
I had a friend who went through something similar but he did everything right and it all happened to work in his favor.
He never outright confronted her but had been suspicious for some time that she was cheating on him, I forget why. Stand up guy who loved his wife but he wasn't going to stick around with a cheater. He didn't have a PI but his XWW was not tech savvy and it wasn't hard for him to find all the proof he needed on her computer which he copied and sent to himself. He also installed a key logger.
He saw a divorce lawyer to understand his options and when he was basically given the okay to move out with no repercussions he found an apartment like two towns away from us (maybe like 25 miles).
So his XWW, who has no idea she's been caught and he isn't giving anything away by his behavior, has an upcoming "work trip" and will be out of town for 3 days. He had the key logger on her comp so he knew it was BS, just a 3 day romp with her lover.
He knew what hotel she would be at and where to have her served. So the day she leaves none the wiser, they say their goodbyes and later that day he, his brothers and another friend (he only told a few people what was going on and I didn't even hear about it until a couple of years after the fact) boxed up all his belongings, furniture he had purchased, etc and moved it to his new apartment.
She wound up being served while in the room with her AP and there was plenty of documented evidence along with the papers so she immediately knew she was caught. She blows up his phone, leaving dozens of messages, texts, etc but he just went completely dark. She comes home to a house that's half empty. And she had no idea where he was staying (although she did go to his job a few times, he would just ignore her and eventually security would make her leave).
But she was pretty much on her belly trying to get him take her back from what I was told. Promised to do everything he needed and how sorry she was blah blah blah.
He didn't have to say one word to her. No confrontation, no asking why, no demanding all the details, no yelling/swearing/name calling, no announcement that he was even filing for divorce.
He said everything he had to purely through his actions. Anyway they got divorced, she tried to get him back for a couple of years before she gave up. This was like 7 or 8 years ago, he remarried and I'm not too sure what she's up to but I heard through a mutual acquaintance she claims to still love him, regrets what she did, and was going to therapy for awhile to deal with the fallout.
Now back when I heard all this happened I thought what he did was extreme and cruel. 4 years of reading stories like this, I know he did everything the right way. Even if he had wanted to reconcile he still made all the right moves. When she saw he was completely ready to drop her, she was begging for a second chance.
If I ever find myself in that situation, that's how I'd want to handle it (although if kids are involved a few things might have to change, fortunately they didn't have any since they were mid 20s at the time).
But at the end of the day it's up to you.
[This message edited by JS84 at 12:49 AM, June 28th (Wednesday)]