thank you so much for commenting! I'm glad the ending stood out for you - it just seems to me that Sam's got a lot of high expectations of himself, and then for him to sink so far in despair and not be able to put the brakes on and then see Dean turn away from him... in this scenario, maybe he'd think the best thing he could do is end it.

He took a lot of meat suits with him. I saw it as a measure of how ruined he is.