Man, that whole Sasuke-Itachi eye transfer arc was wild, wasn't it? After years of thinking Itachi slaughtered their clan out of cruelty, Sasuke finally learns the heartbreaking truth during their final battle - that Itachi was actually ordered to do it to prevent a coup, and spent his whole life protecting Konoha from the shadows. When Itachi deliberately weakens himself from illness and lets Sasuke 'kill' him, he secretly implants Amaterasu in Sasuke's eyes as one last protective measure. But here's the kicker - dying Itachi pokes Sasuke's forehead like in their childhood, transferring his remaining ocular power. Later when Sasuke's eyes get wrecked fighting Danzo, White Zetsu conveniently mentions 'Hey, Itachi's corpse still has fresh eyeballs!' leading to the transplant that gives Sasuke the eternal Mangekyou.
What gets me is the tragic irony - Itachi wanted Sasuke to surpass him without walking his dark path, yet Sasuke basically needed to literally take his brother's eyes to reach full power. That whole arc perfectly encapsulates Naruto's themes of inherited burdens and twisted brotherly love.