One Shall Fall is my all time favourite episode asides from Partners. The fact that it took harming Raf for Optimus to let go of trying to convince Megatron to change, that their war would continue as long as Megatron lived on. The epic showdown between the two long time rivals had me on the edge of my seat until the very end. I honestly did think that Optimus had finally killed Megatron, only to be proven wrong when the Dark Energon made Megatron stronger at the last second. Truly a badass and dramatic episode.