23. Chillblaine
Mark Blaine, a.k.a. Chillblaine, certainly had his place on The Flash but to say he was a fan-favorite would be a bit of an overstatement. He was introduced in season 7 as something of a nemesis for Frost, who was still finding herself at the time, but it was clear that the two were falling for each other.
Their whirlwind and often corny romance didn’t exactly resonate with viewers and didn’t do much for either character. After Frost’s death, however, Mark showed a real desire to grow, learn and evolve to honor his love’s life. But that ultimately resulted in him attempting to bring her back to life.
He became a main character in the show’s ninth and final season in what was really quite a bizarre creative decision. Throughout those 13 episodes, he betrayed Team Flash, ignored Team Flash, and hindered Team Flash (as well as having multiple on-screen absences). But Barry being Barry insisted he could be saved.
He did redeem himself in the end, but fans had grown fed up with the show’s refusal to stop going around in circles with his character development in an already-crowded final season. It’s hard to really know what the point of the character was, but at least he was played very well by Jon Cor.