You literally transmute matter at will, you do not need to fight Killcannon just turn his robot arm into cheese or something. Your nemesis is a villain that you do not need to consider the whole cannot effect living tissue thing for even a second. That is all.
I get frustrated cause that’s exactly what firestorm does. He has the power to transmute matter at will or even cause a nuclear explosion, but this guy instead chooses to fight like a worse possible version of human torch.