The Rampaging Cyborg

No matter what, I cannot die until I have destroyed that rampaging cyborg. To that end, as a cyborg for justice, I must continue to fight evil until I encounter that rampaging cyborg again. I must get stronger!

The Mad Cyborg (狂サイボーグ, Kyō Saibōgu) is the cyborg that destroyed the home town of Genos and murdered his family. Since then it is his archenemy.

Appearance
The Mad Cyborg has a brief appearance during a conversation between Drive Knight and Genos. It appears to look like a humanoid robot.

Personality
The Mad Cyborg is insane and uncontrolled, having destroyed everything in sight at Genos's town. According to Genos, this is probably because a failed body modification generated an irregularity in its brain.

History
Four years before Genos met Saitama, the Mad Cyborg attacked the former's hometown, destroying everything and even murdering his family with Genos being the only known survivor. While tracking down the Mad Cyborg, Dr. Kuseno came to the ruined town and found Genos.

Drive Knight claims that the rampaging cyborg destroyed his village too, and that he thus has a similar past to Genos. He did not give a specific time frame. Drive Knight tells Genos that the Mad Cyborg is a creation made by Bofoi.

It is also revealed by Dr. Kuseno that the Mad Cyborg too killed the scientist's family in one of the villages it went around destroying.

Neo Heroes Uprising Arc
After Drive Knight explains his history about the Mad Cyborg to Genos, it is revealed no hero records have been shown to take down the Mad Cyborg and it has not shown up for a few years. It is theorised that it is most likely in sleep mode, hidden away with the rest of Bofoi's robotic creations.

Abilities and Powers
Although the full extent of what the Mad Cyborg is capable of is unknown, based on what Genos's mentioned, it can be inferred that this rampaging cyborg is very powerful and dangerous. It was able to completely ruin Genos's town, having destroyed everything there including parks, schools, and buildings.