shikamaru
he did get revenge and was ready to leave the village with chouji and ino without tsunade's permission but he took it pretty well
and even helped naruto overcome jiraiya's death
I would have to say Naruto. He always tried to make friends and see the bright side of everything when most people in his situation would have probably become bitter towards others and lead a life of solitude, and Kakashi would be a close second.
The obvious answer is Naruto. He was alone most of his life just like Gaara, but even worse is the fact that up until he became a Genin everyone in the village treated him like scum. He could've went on a psychotic rage but instead he did harmless pranks and is now the most revered shinobi of his generation.