ShiMan12161516 asks: Do you know any tips on how to write an argument so bad that it breaks up friendship ties?
When we meet someone new, we usually have few expectations of that person. We don't know them. The closer we are to someone, however, the more expectations we have. It's much easier for that person to disappoint you.
Disappointments and arguments are bound to happen between friends, depending on the kinds of expectations they have of each other. The friendship will usually endure once they get over what happened. Whether or not they are able to get over it will depend on how much of a violation the action was to a friendship.
Loyalty
One of the most important things that cement a friendship is loyalty. It's the knowledge that, no matter what, your friend is on your side. When you need help, the friend will offer aid. In an argument, your friend will take your side. You know you can depend on this person. The closer the friendship, the stronger the sense of loyalty.
Betrayal
But what happens when the friend doesn't choose you? Maybe they chose a boyfriend/girlfriend or some other friend instead of you. Your expectation is shattered. You feel betrayed. How earth-shattering this betrayal is depends on how close you were, and how lofty your expectations were.
Importance of the Issue
The gravity of the situation is a big factor for when a friendship recovers, or if it will recover at all. If the friend forgot to pick you up from the airport, it's pretty bad, but not something to lose an entire friendship over. If this person sleeps with your significant other, though, that's quite an egregious betrayal.
How to End a Friendship with an Argument
Now that you have a clear understanding of the mechanics of friendship, you just need to find the right issue that fits into your story to serve as the wedge. What's important to the two friends? The things we hold dear tend to differ in priority from person to person. I may value family more than money, while my friend might rank money higher because it means more security in life. Maybe her family was mean to her. Understand what motivates your characters.
Now find a way for these priorities to collide. Let's say my friend has spent her life chasing the next big promotion. It makes her feel powerful and in control, which are things she lacked when she was growing up. The next big thing happens to be a position that my father holds. He's getting old, but doesn't want to retire yet because he loves his job. It makes him happy. My friend sees an opportunity and somehow forces an early retirement, paving the way for her to claim the position.
If I had the same values as my friend, I'd understand the move. I wouldn't be thrilled about her decision, but it wouldn't end the friendship because I might have done the same thing. But because I value family over money, the betrayal is much larger. In my mind, her loyalty extended to my family. When she forced my father into early retirement, however, she committed a crime against me and our friendship.
But in her mind, she wasn't hurting me. It was someone else. Family isn't a big deal to her because her own family is always hurting her. She believes I should understand why this is so important to her. That I should support her decision. So when I don't, when I get angry instead, that makes her angry. She feels betrayed because I'm not on her side.
When the most important values between two people are at odds and feelings are hurt in the process, that's when friendships can suffer or even crumble. That loyalty is lost, and without it, the friends become awkward acquaintances instead. It's hard to have true friendship without trust.