Typhoid Mary: Just like his original counterpart, he spreads the Zero Virus just by existing.
Tragic Monster: "I didn't ask to be born a virus.".
Paradox Person: He's a NetNavi, all right, but he's purely viral in nature.
You'd be forgiven for thinking he's the Big Bad before he starts talking.
Large and in Charge: The largest humanoid Navi in the game, he's easily four times the size of MegaMan.
This is done to distinguish him from ProtoMan, who is already a Zero expy.
Irony: The digital version of Zero looks more robotic than the reploid original.
He also leads the authorities right to the Professor's location in the finale, turning the Bittersweet Ending into a happy one.
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Heel≯ace Turn: If you manage to find the MystData before you face him for the final time, Lan's dad will figure out how to turn Zero into a Navi.
Even he's not sure how that happened, and he's not too pleased about the problems he causes just by existing. Not an infected Navi, a full-blown computer virus that gained a soul.
Grew Beyond Their Programming: He is a virus.
Thankfully, if you have the MystData, there's no need for him to die.
Face Death with Dignity: He holds nothing against Megaman for coming to delete him and, after being defeated, is quite accepting of deletion.
Chuck Cunningham Syndrome: Despite him being canonically okay in the end, he just disappears in the future games without much explanation.
Affably Evil: He is polite towards Megaman, but Zero does not intend to end the Zero virus plague caused by his existence without a fight.
A virus/Navi hybrid of sorts in the Network Transmission game.