- For her Earth One equivalent, see Caitlin Snow.
- "If you knew me at all, you would know that I hate the name Caitlin. I'm Killer Frost."
- —Caitlin to Barry Allen[src]
At one point in her life Caitlin met and married Ronnie Raymond. Around 2013 Caitlin and Ronnie were affected by Harrison Wells' S.T.A.R. Labs particle accelerator, giving her cryokinetic abilities and him pyrokinetic abilities. Since then, Caitlin cut off all ties to her past life and began calling herself "Killer Frost" and refused to use her real name. Even so much as hearing it made her angry.
The arrival of Earth One Flash
After Cisco Ramon/Reverb vibed that his doppelgänger, along with other Earth One residents, had arrived on Earth Two, Killer Frost and Deathstorm searched for them. The two went to Jitterbugs and asked everyone which one of them were in the wrong universe. When Barry called her Caitlin, she told him she no longer went by that name. Killer Frost then fired icicles toward Barry, who used a table as a shield. After Ronnie critically injures Joseph West, Caitlin and Ronnie were brought outside while Iris was distracted. After failing to kill Barry, Killer Frost told her husband to do the job. The Flash used a helmet from a statue of Jay Garrick to redirect fire hurled by Ronnie toward Caitlin and badly injured her, and she was taken away and tended to by Ronnie.
Later, Caitlin and Ronnie were approached by Iris, Floyd Lawton and Cisco Ramon/Vibe, Reverb's doppelgänger, though she and Ronnie made the three stand their weapons down. When Reverb tried to get Vibe to join him, the Flash intervened. The Flash was eventually overpowered by both Reverb and Deathstorm but Killer Frost warned them that Zoom told them to make sure the Flash was left unharmed. Zoom arrived and killed Ronnie and Reverb, much to Killer Frost's dismay. She was approached by Zoom but was told the latter was happy one of them knew their place. After Zoom sped off, Caitlin ran toward her husband's body but soon ran away in grief.
After Ronnie's death Caitlin fled into the woods to mourn but was soon approached by Iris, Harry, Cisco/Vibe and Earth-2 Barry, demanding to know where Zoom was but she refused to tell him. Instead Killer Frost tried to kill them and bring them to Zoom but Cisco eventually held her at gunpoint and Caitlin surrendered. However she still refused to tell them where Zoom and Cisco tried to reason with her, telling Caitlin of her Earth-1 counterpart and how compassionate she is and how distraught she was when her Ronnie died too. Upon hearing this Caitlin was convinced to aid them and took them to Zoom's lair.
Though Caitlin freed Jesse she was unable to free Earth-1 Barry she wasn't able to penetrate the carbine glass, but eventually managed to phase his way out on his own. However Caitlin has secretly called Zoom and he showed up as soon as Earth-1 Barry escaped. However when Zoom told them all that though he couldn't kill Earth-1 Barry or Harry he could kill everyone else, and started with Jesse. However before Zoom could kill her Caitlin turned on Zoom and blasted him with her ice powers, and held him down long enough or everyone else to escape. What became of Caitlin afterward is unknown.
- Cryokinesis: Caitlin has the ability to freeze air around her hands and form it into icicles or other sharp objects. Killer Frost is also capable of creating objects such as a bridge by shooting ice from her hands and was able to shortly hold off Zoom using the same method. She can also freeze an entire human body with just a kiss, though it is implied that she cannot control this, thus limiting her to only being able to kiss people with extreme body temperatures such as her late husband.
- Since Caitlin of Earth-One specifically stated in "King Shark" that she does not possess the metahuman gene, the fact that Caitlin of Earth-Two was able to become a metahuman is the first indication that there are more subtle differences beyond contrasting events.
Behind the scenes
- Killer Frost is an alias used by three different female metahuman supervillainesses, all of whom were enemies of Firestorm in the main DC Comics continuity. In the pre-Crisis on Infinite Earths timeline, Crystal Frost (introduced in Firestorm: The Nuclear Man #3, in June 1978) was a college student in love with Martin Stein who became the first Killer Frost after a freak accident which imbued her with the power to absorb heat and generate cold. After her death, a new Killer Frost debuted as Dr. Louise Lincoln (in Firestorm #21, in March 1984) a friend of Crystal's who gains the latter's powers through the same means in order to avenge her death. This incarnation of the character made several appearances up until the New 52 relaunch, having been a member of the Injustice League, Secret Society, Suicide Squad and an independent contractor. During the Forever Evil crossover-event of the New 52 relaunch, Caitlin Snow was introduced as the latest incarnation of the Killer Frost persona (as Caitlin Snow in The Fury of Firestorm: The Nuclear Man #19, in June 2013, and as Killer Frost in Justice League of America #7.2, in September of the same year). This character is a S.T.A.R. Labs scientist in the field of thermodynamics, working in the Arctic.
- The Arrowverse version of Killer Frost, although identified as Caitlin Snow, also shares the Crystal Frost version's affection towards a member of the Firestorm/Deathstorm entity, in this case Ronnie Raymond.
- When confronting Killer Forest in the forest after finding her, Cisco called her "Elsa" as in Disney's Frozen's Princess Elsa due to her blonde hair and ice-manipulation powers. This has since become one of the fans of the show's most beloved jokes.