Spider-Man

After  Peter Parker  was bitten by a radioactive spider, granting him arachnid-like powers, his uncle was murdered by a criminal that Peter could have stopped earlier. Feeling responsible, Peter became the vigilante  Spider-Man.

Origin
Peter Parker was bitten by a radioactive spider while in highschool, granting him spider powers. After seeing his amazing powers, he developed two wrist-mounted web shooters. Upon the death of his Uncle Ben due to Peter's indifference, Peter learned by his uncle that "With great power there must also come great responsibility", and thus became the vigilante Spider-Man.