Toxic Chainsaw

Super Venom Chainsaw is a villain in Boku no Hero Academia. He critically injured All Might to the point that he almost died.

Appearance
Nothing is known about his appearance since he has yet to make an appearance.

Personality
Nothing is known about his personality. However, since he is a villain and seen the reaction of someone who is knowledgeable about the heroes and villains it's most likely that he was ruthless and cruel as he is still feared now.

History
Super Venom Chainsaw once fought against All Might 5 years before the main storyline. This fight left All Might with a terrible injury.

He is still known by some people, as shown when All Might mentioned him to Izuku Midoriya and he reacted by trembling fearfully.

Quirk
His Quirk is unknown, however, it is assumed to be powerful enough to injure All Might to the point of almost dying and debilitate him to his current state. In short, his Quirk is a force to be reckoned with.