The Lizard is Dr. Curt Connors. He is a supervillain.
Curt Connors was born in Coral Gables, Florida. He was a gifted surgeon who enlisted in the army and was sent off to war. He performed emergency battlefield surgery on wounded GIs, but his right arm was injured in a blast and had to be amputated. After his return to civilian life as a research technologist, he became obsessed with uncovering the secrets of reptilian limb regeneration and studied reptilian biology extensively. From his home in the Florida Everglades, he finally developed an experimental serum taken from reptilian DNA. He successfully regrew the missing limb of a rabbit and then, despite the warnings of his wife Martha, chose to test it on himself. Connors ingested the formula and his missing arm did indeed grow back. The formula had a horrible side effect; Connors was subsequently transformed into a reptilian humanoid monster.
A repeating pattern occurrs, with stress or a chemical reaction turning Connors into the Lizard, Spider-Man fighting him, and then forming some kind of temporary cure to reverse the transformation until the next time. A second personality has formed with the Lizard, one with the familiar goal shared by many villains of taking over the world. The Lizard envisions a world where all humans had been transformed into (or replaced by) super-reptiles like himself. Despite the Lizard's overall hatred of humans, he was often shown to be unwilling to harm his wife Martha or young son Billy.
As Connors, he aided Spider-Man in defeating the Rhino, but accidentally transformed himself into the Lizard and was restored by Spider-Man.
After Connors' return from the Secret Wars event, his wife took their son Billy and separated from Curt.
Tragedy later struck again in the Connors family - this time for Martha and Billy. Both mother and son were diagnosed with cancer after years exposed to carcinogens from living near an industrial lab of the Monnano Corporation in Florida. Spider-Man assisted Curt in successfully forcing Monnano to admit their environmental culpability. However, Martha succumbed to the cancer and died. Billy recovered but remained bitter towards his father. Curt's guilt and internalized anger at these events eventually led him to become the Lizard and attack Spider-Man once again. After reverting back to his human form, Curt purposefully attempted a bank robbery so he would be sent to prison. Curt's stint in prison was short-lived; he was released and transformed into the Lizard once again as part of a scheme by Norman Osborn, a.k.a. the Green Goblin, to form a group of villains to kill Spider-Man.
When Connors is transformed into the Lizard, his strength is increased to superhuman levels. Likewise, his speed, stamina, agility and reflexes are also raised to a level equivalent to that of Spider-Man. He can also scale walls using a combination of the scores of sharp tiny claws on his hands and feet to create adhesive pads like those of a gecko lizard, and micro-scales that create molecular friction. He is highly resistant to injury due to his thick scaly hide, allowing him to resist punctures and lacerations from ordinary weapons and lower-caliber firearms. In addition, the Lizard has highly enhanced healing abilities which allow him to quickly recover from grievous wounds, including regenerating lost limbs. He also has a powerful tail which he can whip at high speeds. The Lizard has razor-sharp teeth set in muscular jaws that can deal a lethal bite. Like a reptile, he has cold-blooded characteristics and is therefore sensitive to drops in temperature; a sufficiently cold environment will cause his metabolism to slow drastically and become dormant if he is exposed to cold temperatures for too long.
The Lizard can mentally communicate and command all reptiles within a mile of himself via limited telepathy. He has also on at least one occasion secreted powerful pheromones which caused nearby humans to behave violently.
Based on various physiological and environmental factors, the Lizard's intelligence can range from bestial and animalistic to normal human intelligence. The Lizard personality has most often manifested with human intelligence, capable of speech and higher reasoning. However, the Lizard is rarely as intelligent as Dr. Connors is in human form.
He is an enemy of Spider-Man.