Previous ex, we were going on a few years. Being much less experienced in relationships than I was, she was unable to distinguish what things were actually worth arguing about; therefore, we argued about almost everything. I let the relationship continue longer than it should have (I had just got back into the committed game after a lengthy hiatus, so I wanted to atleast try and make it work, and have her mature through it.)
Anywho, I remember this one argument, in the middle of it all she said something like "so we're done? are you done?" I paused for a bit and I just replied with "................yep!

"
And that was it, just like that. The argument was no different than the rest, I was no more heated than the rest. I just had enough. No attempts at reconciliation, did not try to work it out. It literally ended at that moment. Both moved on and became cool later. When talking about the breakup she said "I honestly didn't expect you to end it just like that"