Elijah Snow (please log in to view the image)
Abilities: Cold Manipulation, Ageless, tutored in detection by Sherlock Holmes, peer to ultimate super-spy John Stone, Snow is a master strategist. Snow has demonstrated the power of heat subtraction (appearing to make his environment colder), a devastating ability when applied with intent.
vs
Killer Frost (please log in to view the image)
She have shown the ability to absorb heat from external sources and transmute it into waves of cold. Using these powers Killer Frost can create an ice-sheen across her entire body, and generate objects composed completely of ice, such as projectiles (ice daggers) and defensive walls. She can also instantly freeze animate matter through physical contact
Problem for snow is that he has few feats with his power, resorting to strategy and tech to get the job done, but I think he was extremely powerfull. Without any prep KF would probably take it, as she has a lot more feats. But Snow could turn the results arround with even a marginal amount of prep for both of them.