If they knew my SO was taken I'd have words but like, my SO is the one meant to be loyal and not some random other person who might not have have even known
Only if I already had some sort of relationship with the person. But the issue is primarily with the partner.
True story:
I messaged her on Facebook. She didn’t know about me. The dude was making plans with both of us on the same day, her in the morning and me in the afternoon.
We decided to get brunch that morning and then go together to the place he was meeting her at. He got mad and left. We stayed, got hammered, and then got our nipples pierced together.
I wouldn’t do it this way again. It turned out okay but it wasn’t a mature way to deal with it.
it wasn’t a mature way to deal with it.
The lack of violence or bad reaction is very mature IMHO.
That’s fair but I should have talked to the cheater about it instead.
I'd fuck them, to show my dominance.
We didn’t bang but we did get our nipples pierced together. Close enough.
Doesn't that make it rather difficult to walk?

Pierced - together??
Like we did it at the same time in the same room. I saw her boobies. 😂
The other person is not the problem or the culprit. I would look into my own relationship and confront my SO, be furious, maybe aggressive (but not violent, that I would never be), maybe crying.
The other person it's a distraction, it your SO and yourself you need to focus on.
It does kind of depend on who it is, imo. If it really is some random person who might not have even known about our relationship, then no. It's not their fault or their responsibility.
But what if it's your best friend? Then definitely. Both out of my life.
What I mean is that it's not your best friend fault. It's your relationship that has issues to be addressed or your SO would not have looked somewhere else.
So I can be enraged with my best friend, indeed, like with a stranger, but make no sense to address him or her when the fault is not their fault.
When somebody cheats the issue is within the relationship and or the cheating person. The third person is just an external factor, if not your best friend it would have been another person, see, it's irrelevant.
Irrelevant? Like hell it is. My best friend also has agency. They make their own choices, just like my partner. And in that moment, they both chose to screw me over.
Now, we could of course have a debate about who should get more of the blame, but that's besides the point. When it's a random person, they have no ties to me. I don't trust them, love them, feel any connection to them whatsoever. They can't 'screw me over' because they don't know me. But my best friend? Our friendship would forever be ruined and I don't think you can call that irrelevant.
There is a huge difference between your best friend and your partner. But maybe I am looking at it from 50 years of life, quite a few partners changed over time, where I have been cheated on or I have cheated on. And also where nobody has cheated on.
So I see things less black and white.
What I have learned is that cheating comes when there is a problem in the relationship, not the other way around. Never.
So first and foremost you look at your relationship then look outside. Or you will only repeat the same cycle that lead partner to cheat with the next partner.
Should you hate your best friend? Yes I guess... Should you hate your partner? Yes I guess. Should you blame them? No. Relationship is two people, and you are one of those two people. So blame also yourself as much as you blame partner, and maybe the third person
But always the fault in cheating lays on BOTH you and partner first and foremost. And trust me: you have 50% of the blame even if partner is the one that cheated. He, or she, of course fully bear the other 50%.
The third person might be a bastard that took advantage of the situation or maybe genuinely fell in love with your partner. But that person has no blame in the cheating
I am talking experience and real life cheating, not theorical hypothesis here.
No.
Just break up like a normal couple.
And no matter what anyone says or does...
DO NOT GET BACK TOGETHER
I called and asked him WTF, but he was my best friend at the time, so, maybe not a typical situation.
Nah, just drop both of them out of my life. Break up, block phone numbers etc.
No need to keep trash around. No need to have drama.
Nope. They are not the problem.
It is always on the cheater, you have the promise of faithfulness with them - no one else responsible for other people decisions.
For all they know, they had a good romp. Imagine some random person coming up to you and punching you in the face the next day. It doesn't compute.

My partner, with whom I assume you mean I had a sexually exclusive relationship, I'd leave in a heartbeat. The things I'd do to them in my mind though...
CW: blood

Image belongs to 姫 on Pixiv: https://www.pixiv.net/users/5874587
I had this happen to me and my good friend.
They kept it a secret for a year and I only found out from another buddy of mine. I promptly dumped her and stopped talking to the friend. He later bragged about it my friends and then for some reason threatened to hurt me. I took the messages the police and inadvertently got him deported. I didn't know at the time but he was an illegal alien who overstayed his student visa. Oops.
He later apologized to me after for the hurt he caused. I also told him I felt hella bad for accidentally deporting him.
Nah, I'd just leave. If the "loved one" decided to cheat, then there wasn't a relationship in the first place. Wish them well, grieve the relationship, go back to your own life adventure.
Unless there are kids and a mortgage or something. Then, things get complicated. But the breach in trust is unfixable, so the relationship is dead anyway.
No
Nope.
The third party isnt the problem. It's your SO that cheated, and who should suffer.
Pack up. Leave. Take what you can.
No. Fuck no.