The tragedy of Steve witnessing Bucky's almost death more than once and see him fall to death twice and Steve's desire to die rather than live without Bucky really is something so special
Steve goes on a suicide mission to save him cause he'd rather die trying than knowing Bucky might suffer
Bucky falls off the train
Steve crashes the plane into the ice cause he can not live with that guilt (yes he could've jumped before crashing and I don't take any other opinion on that)
Bucky fights him as the Winter Soldier on the helicarrier
Steve orders to destroy them while he's still there cause
- he won't leave without Bucky
- he rather die than leaving Bucky behind again
And then he stops fighting cause he rather die by Bucky's hand than causing him any more harm
He rather die by the Winter Soldiers hand than witnessing Bucky truly gone
And then he watches him dust away right in front of him and again he can't do anything about it
I know I'm saying nothing new here but it just hits me every time
Their relationship is so fucking meaningful and deep
To say it in Cevans' words:
"You can take it however you wanna take it, but fact is, it's a love story"
Bucky is his home in every sense
(and this is why he never ever would've left Bucky behind)