Dean's love for Castiel is literally something you can chart the growth of with data points. Just using Dean's reactions after each time Castiel dies.
Season 4: oh wow he died doing the hottest thing ever ('making it up as we go.') Nice.
Season 5: (no time to react before he's back) Are you literal god??
Season 7(first time) denial, then cursing cas out for his choices (ie, choosing crowley instead of dean... Big Feelings on display)
Season 7 (about 3 seconds after the first time in season 7): I'm going to be upset about this the rest of the year, have full on nightmare ptsd from it, and project it onto every relationship and interaction in my life from now on.
Season 8: I will be so traumatized by this that the memories won't even form properly and I won't even be able to SPEAK ABOUT IT AT ALL. Period.
Season 9: only about 6 seconds before he's back, but still a significant amount of wailing his name.
Season 12: depression, rage, eventual suicide
Season 15: Sobbing hysterically. Not even caring that Sam is calling because everyone is dead. Not giving a fuck about any other actual thing in the rest of the world no matter the stakes. Followed by:
'Castiel wants me to live, and I suppose I've internalized the message that I am not a terrible, unworthy person, so I will live and not kill myself so that his sacrifice means something. J/k thank god a fucking rebar. Don't call an ambulance. Don't bring me back. Please let me die.'
We need a chart. I need a chart.