I ASSUME YOU MEAN OF HIS OWN, rather than including Sasuke's. :T That would be the clan massacre memory. Hands down it was the worst in his registry. Everything about it was terrible. He killed his family. He mindfucked his brother and made him hate him. And he knows it pretty much ruined everything forever.

Do you think Sakura will ever decide to use her name, or will she stick with Tsunami? (or is it too early to know)