Caitlin Snow is Frost (formerly Killer Frost), a scientist with cryogenic powers. Though she started out as a villain, she has since reformed, and even joined the Justice League of America.
There are roughly one-sh*t billion tropes so PLEASE look through them before adding one. Otherwise add what you like. ADDITION: PLEASE read through the trope description provided before submitting something. It's not a huge deal but too often people submit characters that don't fit just because they misinterpreted the title...
