At the night of Itachi destoried his family, Sasuke has become a totally revenger in my opinion,. He stay in Konoha just want to become strong enough to kill his brother. But after learning from Kakashi and any others, eh found that this power cannot satisfied him because he sdtill too weak to beat Itachi. Then he choice to study with Orochimaru and almost all relationships among his past.
At the second prat of naruto manga shippuden, Sasuke become more cool even cold than before, he killed Orochimaru, beat DIdara, and finally fight with Itachi. After the death of Itachi, he meet with the man called Madara. Madara told him all the "truth" about Itachi, he killled all his family after the order of Hokage and Konoha. It's a big shock to Sasuke, he then decided to join in Akatsuki and try to destory Konoha by himself. Disturb the Five Kage meeting, kill Shimura Danzou until the break of Forth Ninja War he meet with his brother again, he has changed a little.
He never show his truly himself to others until he remeet with Itachi, he turn himself into a really little brother I think! And I believe that this battle between Kabuto will become the important change point of Sasuke!Of course the last meet of Naruto and Sasuke is the destiny, but he can also influenced by Itachi!