Leonard Snart (Arrowverse)

Leonard Snart, also known as Captain Cold, is the tertiary antagonist in Season 1 of The Flash and a supporting protagonist/anti-hero in the upcoming TV series DC's Legends of Tomorrow. He is a supervillain with a freeze-ray and seeks the thrills of robbing and killing.

Early life
Snart's father was a corrupt police officer who frequently abused him and his sister Lisa. As a child, he and Lisa were taken by their grandfather to a diner called Motorcar, which they would use to spy on police officers later on. He eventually dropped out of high school and started sticking up banks with a gathered crew. Every six months, Snart would case a place worth robbing in Central City and then leave after getting his target. He eventually landed on a list called Central City's Most Wanted. He worked with a guy named Mick Rory, which ended badly for Mick and Snart refused to work with/for him again.

Kahndaq Dynasty Diamond heist
In 2014, Snart and his crew came to Central City to hijack an armored car in order to acquire the Kahndaq Dynasty Diamond at the city museum. They use a tow-truck to stop the car and got the doors open with lost of liquid nitrogen, but then comes the Flash. He quickly took down the robbers and Snart shows his face to his victor, then one of his henchmen shoots a security guard in the shoulder. Flash takes the guard to a hospital and Snart gets away from the scene. Back at base, Snart's henchmen spat out theories about the Flash, one even claiming that he is a drone. Snart noticed that the response time from the car was 182 seconds, rather than 60 seconds with a bank. He berated a guy who wanted to quit the job and killed him, then told his men that they need to "up [their] game".

Snart met arms-dealer Basil Nurblin and he offers him a fire-based weapon. He refuses to take it, since he "did not need to heat things up, but slow them down". Basil gave him a freeze-ray stolen from S.T.A.R. Labs, and upon hearing only he knew of the freeze-ray, Snart froze Basil to death. He then goes on two tours around Central City Museum to get the scope on the Kahndaq Diamond he sought, and caught the attention of the museum owner, Dexter Myles, who calls on Detective Joe West to spy on him. He tracks Snart until he realizes that he is being followed and freezes the road under a newly-arrived police car and ran into a nearby theater to escape. Snart attempted to freeze West, but Flash appears and gets frozen instead. He then tried freezing numerous people around the area and Flash had to save them, unable to stop Snart from freezing a security guard at the theater, and runs away while Flash feels guilty for not saving the guard.

Back at base, Snart told his last two men that tonight, they still the Kahndaq Diamond. The guys protested, since now the museum would be filled with police, but with a freeze-ray they'll get the Diamond, as Snart knew that random bystanders was Flash's weakness. His men still disagreed and left Snart on his own, who went to get the Diamond himself, which he does successfully, and heads to the Central City Train Station, where he got into a gunfight with Joe West and Eddie Thawne. He escapes on a train, but then comes Flash to get the Diamond back into the museum. Remembering Flash's weakness, Snart froze a train car full of people and had it derailed, leaving Flash to save the guys on the rain while Snart would get away. He got everyone off the train and then gets shot in the back by Snart, who thanks Flash for getting him to up his game. Suddenly, S.T.A.R. Labs employee Cisco Ramon appears claiming to be holding a freeze-ray (which was actually a vacuum cleaner with LED lights). Snart, after being called Captain Cold by Cisco, leaves with the Diamond and then met Mick Rory and convinced him to step up his game as well now that their playground has been invaded by the Flash. He gives Rory the flamethrower that he took from Basil and he became Heatwave.

Getting Flash's identity
Despite the blog done by Iris West containing photos of Flash, he was still called an urban myth. Knowing that he would make it harder to do criminal operations, Snart schemed a way to get the entire world aware of Flash's existence. He lied to Mick that they were going to steal expensive cars from a garage when actually Snart sought to fight Flash again. However, upon noticing that Flash was nowhere to be seen, he and Mick left without any of the vehicles. Their second attempt to get Flash aware of their return to Central City was by stealing an expensive painting called Fire & Ice from Osgood and Rachel Rathaway (parents of Hartley Rathaway), which was worth $25,000,000. The CCPD arrived with shields made by Harrison Wells from S.T.A.R. Labs that were invincible to Snart's freeze-ray, but Mick's flamethrower was not something they hadn't prepared for. Seeing that Flash STILL wasn't here, Snart and Mick took the painting and ran away. He kidnapped S.T.A.R. Labs worker Caitlin Snow and finally got Flash's attention. She was rescued by Joe West and Snart challenged Flash to a battle in Central City, declaring that now the world will know he exists. Snart and Mick were taken down by the speedster and imprisoned, only to be saved by Lisa.

The three get back to Central City and get captured by a mafia boss named Santini, but they escape and kill his henchmen. Snart tells Santini that he is in charge now and leaves, prepared to get Lisa a weapon from S.T.A.R. Labs. They kidnap Cisco (who previously made Snart's freeze-ray) and his brother Dante and force him re-create their weapons, as well as get a weapon for Lisa, one that "fits [her] personality". Once they got their weapons, they went to a casino and fight the Flash, who backs off once Snart tells him that they have Dante and Cisco. Back at their base, Snart tortures Dante by freezing his fingers fatally and would keep it up until Cisco told them Flash's real name. He gives in eventually and reveals him to be Barry Allen, Joe West's adoptive father who got his powers from getting struck by lightning on the day of the Particle Accelerator accident. He re-fights Flash after an attempted heist and threatens to tell Central City who he really is, but Flash gets him to stop killing and stealing or else he goes into the Accelerator, which has been converted into a meta-human prison.

Moving the meta-humans
Flash convinced Snart to help him get several meta-human prisoners from the Accelerator out of Central City so they wouldn't be destroyed when Wells (now revealed to be Eobard Thawne) re-activates the Accelerator and get back to his own future timeline. Snart refuses to unless he breaks into the CCPD building and grab all knowledge and files on him, which he does with Lisa. Snart gets the meta-human prisoners over to a Ferris Aircraft runway (where they mention the company closing after one of their test pilots went missing) in a truck and then betrays Flash by letting the prisoners out and getting Mark Mardon to destroy the plane that would take them to the island of Lian Yu (where Oliver Queen/Green Arrow spent 5 years of his life on). All the meta-humans tried killing Flash and then Snart kills Jake Simmons, claiming he owes the freezer money. He tells Flash that now the prisoners owe him and gets them to join his "Rogues". He and Lisa drive away in a motorcycle.

DC's Legends of Tomorrow
Captain Cold is confirmed to appear in the 2016 TV series DC's Legends of Tomorrow as a supporting protagonist as one of the people gathered up by Rip Hunter to battle Vandal Savage.