Haku used himself as a human shield against Kakashi's Raikiri to protect Zabuza. When Zabuza revealed that he really did care about Haku, he valued him higher than a simple tool. He wanted to die for what he did, then took one kunai from Naruto and charged through Gato's men to get to Gato, being stabbed multiple times along the way. Upon reaching Gato, Zabuza killed him, and collapsed due to his injuries. Zabuza asked Kakashi if he could be brought to Haku, to which Kakashi complied. Being by Haku's side in death, as Haku was by his in life, Zabuza wished that he could go to the same place as Haku.

Is that ENOUGH?

Haku died to save Zabuza fron Kakashi's Raikiri...while Zabuza died after fighting Gatou's thugs(read the manga dude).

i think its..............................
naruto.

kakashi kills haku and the gang on the bridge kills zabuza

kakashi kills haku and gato's men kills zabuza plain and simple

Does this count the Akatsuki in?

Kakashi kills Haku on accident when he was thying to kill Zabuza, then an angry mob of theives and criminals killed Zabuza