Doctor Curtis Connors was a scientist who lost his arm in an explosion. Using his scientific knowledge, he searched for a possible way to regrow his limb and created a serum using the DNA of reptiles. He tested the serum on a rabbit, resulting in it regrowing a missing leg. In hopes of restoring his arm, he used the serum on himself and his arm grew back. However, the reptilian DNA in the serum mixed with his own, and he transformed into a monster called The Lizard, who plotted to take over the world with the help of an army of reptiles. However, he was stopped by Spider-Man, who forced him to swallow an antidote and change him back into Curt Connors. This did not get rid of the Lizard permanently though as Curt kept on changing back under certain situations. However, Spider-Man was always there to save Curt from the Lizard.
Connors Formula: After injecting himself with a special serum to regrow his arm using lizard DNA, Curt transformed into a giant reptilian creature that granted him several powers.
Superhuman Strength: Connors' strength is enhanced when he transforms into the Lizard. He is able to throw cars and uproot trees with no difficulty.
Superhuman Durability: The Lizard's tough, scaly skin is hard to penetrate, making him very durable. Spider-Man, who can punch through steel and lift 10 tons, hurt his fist when he punched the Lizard in the face.
Superhuman Speed: The Lizard is not only strong but also fast. He can keep up with Spider-Man, who can run at 200 mph and claims the Lizard is just as quick as he is.
Regeneration: The Lizard has a healing factor, as demonstrated when Curt regrows his missing arm every time he transforms. He even claims he could regrow his arm again if it were to be torn of.
Fangs & Claws: When transformed, Curt's teeth and nails grow to be very sharp, easily capable of slashing Spider-Man. He has used the claws to climb up walls on multiple occasions.
Reptilian Telepathy: The Lizard can communicate with reptiles such as alligators and snakes using his mind. He can use this to dominate the creatures,
Vast Intellect: Due to his previous experiences as a biochemist, Curt has proven himself to be a genius in intellect.
Extreme Temperatures: While Connors' lizard transformation offers him many great reptilian powers, it also makes him inherit their cold-blooded nature. Thus, the Lizard is particularly vulnerable to very hot or cold temperatures that could do severe damage to his innards, easily stunning and potentially killing him.