Sometimes referred to as "Bomber Zero". He was found by Misty.

When he is first awakened by Misty, he seems to suffer from amnesia. He didn't know who he was, but continuously kept getting flashbacks relating to Mighty. All the characters besides Misty assume he was Max, brought back to life. This was until Max attempts to take out the Jetters in one go, when Zero arrives and stops him. Eventually, he regains enough of his memory to remember who he is (or rather, who Mighty was) and visits Momo on his own.

It is later revealed that he was a prototype unit for Max built by MechaDoc. He was created to absorb data from Mighty so that MechaDoc could learn the Bomberman's secret, or at least their ability to use bombs. When Zero absorbed Mighty's data, just before Mighty destroyed the Hige base, Zero absorbed too much data, absorbing both his memories and his heart and became just like Mighty. With this, he was able to use Mighty's powers and shared similar personality traits. When he awoke in MechaDoc's lab after escaping the base just as it exploded, he instantly recognized and rebelled against MechaDoc, but his power was cut before he could take any action. MechaDoc left him in the remains of the Hige base where Mighty was killed, until he was discovered by Misty.

Zero defeated Max in combat but became possessed by his spirit. White Bomber defeated Zero in this form and caused enough damage to defeat Max's spirit, but caused Zero to die in the process. Zero gave White Bomber a final gift which was a recording of Mighty's final moments for all to see.

[Source: Bomberman Wiki]