Season 3 is just proof over proof of how Klaus really did care about Stefan, simply through the sheer amount of sass he is allowed to have.
Like, yes, you can make an argument that klaus enjoys the banter, but then Stefan pulls the " some kind of master race" and barely gets a " watch the attitude " in return. And klaus IS bothered.
Stefan betrayed Klaus like what, 3 times before the mind control?
When in Mystic falls, Klaus could've killed him thrice over, but noo, just neck breaking, because Originals are petulant children.
When Mikael comes and Klaus picks up the phone, Klaus is downright giddy to talk to him. Stefan is suffering, because humanity or not, that is bred into his being, and Klaus is there like " let me tell you about my day!"
Stefan " your dad's dead"
Klaus " if you lie to me, I'll know, so swear on your life"
He was almost asking Stefan not to betray him again, so he wouldn’t have a reason to kill him.
This man fucking imprinted onto the resident " vampire w familial issues and trauma" magnet