What do you think about me unintentionally causing an argument between a couple; which I then found out almost broke them up?
Why did you want to cause an argument?
I later felt guilty about it.
If you think you were responsible for the argument, you should apologize to them. It'd great if you bring them together again.
I almost fucked up their relationship because of my impulse to say some shit, I don't deserve to live.
It's great that you realize your mistake. It would be great if you acknowledge your wrong doing to them. This may help you to forgive yourself as well and move forward.