- "“Be good, Leo”
- "Leo Snart and Barry Allen"
- —Crisis on Earth-X, Part 4
Leonard "Leo" Snart is a rebel from Earth-X, serving as a member of the Freedom Fighters. He is the boyfriend of Ray Terrill. After meeting the superheroes from Earth One, he decided to join the Legends, using his skills at psychotherapy to help them with the loss of Martin Stein, while grieving about his own loss of Mick Rory.
At some point Leo became a member of the Freedom Fighters, a group openly opposed to the Nazi rule over Earth-X. He was a freedom fighter alongside his best friend, Mickey, growing up together in the resistance. When Mickey died, saving police officers from fire, Leo was devastated, a grief he kept with him up until meeting Mickey's counterpart from Earth One, Mick Rory.
Leo saved Ray Terrill, Oliver Queen, Barry Allen, Jefferson Jackson, Martin Stein, Sara Lance and Alex Danvers from being killed by a firing squad commanded by a Sturmbannführer. Leo and Ray helped the team reach a breach located in a Nazi base to return to Earth One where they participated in the defeat of the Nazis, Eobard Thawne, Oliver and Kara. In the end, Cisco Ramon breached Ray back to Earth-X, though Leo chose to stay behind on Earth One for a bit and later attended Stein's funeral where he held onto Mick Rory while Mick was crying, telling him to let his feelings out. Following the Crisis, he bid a temporary farewell to Ray Terrill and the Freedom Fighters, deciding to explore Earth One, joining the Legends.
Leo is shown to highly despise the Nazi rule over Earth-X. He is an optimist and a bit of a show-off, chastised for his risky "dramatic entrance" by Ray Terrill. Like his Earth One counterpart, he is extremely sarcastic, and also has a flirtatious streak, flirting with Sara Lance and Oliver Queen. Nevertheless, he can be serious at times, especially when the situation concerns his boyfriend, Ray Terrill, whom Leo loves dearly. Also unlike Leonard, who follows "four rules" when it comes to planning: "make the plan, execute the plan, expect the plan to go off the rails, throw away the plan", Leo prefers to carefully (even obsessively), plan his strategies, and stick with that plan regardless. He has shown a peculiar aversion to chaotic fighting, claiming that Mick Rory "can't just go around roasting people" without due process, even though the two were in the middle of fighting Schutzstaffel troops. Leo is also quite adventurous, finding Earth One to be lovely and deciding to stay and explore this new universe. In all, Leo is different from his Earth One counterpart, having an optimistic and chipper attitude that even Earth One Leonard at his most heroic never truly possessed.
Powers and abilities
- Marksmanship: Leo is a proficient marksman, primarily using his Cold Gun.
- Psychotherapy: Leo was trained in psychotherapy and tried to use his skills to help the Legends, grieving over the death of Martin Stein, and especially Mick Rory, whom he found to be having alcoholism-related problems.
- Martin Stein puppet: Leo Snart had a puppet of Martin Stein to help the Legends grieving over Martin's death. He got rid of it when he discovered that it wasn't helping and due to Mick Rory being scared of puppets. 
DC's Legends of Tomorrow
- In the DC comics, Citizen Cold is the identity of Leonard Snart from the Flashpoint timeline. Much like the series, Citizen Cold was a hero who replaced the Flash as the hero of Central City. Unlike the series, the DC comics version had little to no regard to the law, even killing Wally West when he was investigating him for Iris.
- Citizen Cold uses the same visor that Captain Cold wears in the DC comics, while his Arrowverse version used to wear a pair of blue goggles.
- Leo is the first member of the Legends who doesn't originate from Earth One.
- Unlike his late Earth 1 counterpart who was mentioned in passing as pansexual. Leo completely identifies as homosexual - a gay man.