Nates..... (SPOILER)
Nate's death was one of the most heartbreaking things to take place in this series. That's really hard to do considering all the tragedy and loss that happened on the show as that's what the show at it's core is partially about.
I did love at his funeral that although David and Nate fought nonstop at first he was the one most broken by his death and could hardly stay at his funeral.