13. Frost
The most recent installment on the list, Frost’s death came in The Flash season 8. That’s pretty late in the game to kill off one of your strongest supporting characters, but if you’ve been watching the legendary show’s more recent seasons, you’ll know that logic isn’t its strongest aspect at this point.
She may have debuted on the show as a villain but Frost (formerly known as Killer Frost) became an integral part of Team Flash. She died a hero in season 8 when she battled Deathstorm and defeated the evil entity. It was a sacrifice she was willing to make to save her sister Caitlin, but it was one that the show didn’t need to do given that there were far less interesting characters on Team Flash that the show could have survived without.
Nevertheless, it did make for an incredibly emotional moment when Caitlin wasn’t able to save her. Though she tried absolutely everything, Frost’s body just couldn’t go on after the battle and her ice healing factor wouldn’t kick in. Even though many of us knew it was coming, audiences couldn’t help but feel heartbroken as Caitlin desperately tried to save her and Barry looked on helplessly.
To its credit, The Flash made Frost’s death a very impactful moment (which is the very least that she deserved). The same can’t be said for how it handled the potential death of Caitlin Snow herself in season 9. And looking back now, it was clear that this was simply executed to set the stage for the arrival of Khione. Danielle Panabaker is great at playing all three characters but Frost was the one full of the most unrealized potential, and the fact that the show gave up on delivering that potential is almost as heartbreaking as her truly emotional death.