I was never a fan of the Combiner Wars mold. I always felt it was too big.
That one was clearly meant to be just G1 Megatron, and the retool just looked silly if you ask me, which is why I never got him, thou I would say the best Megatron in mainline based upon his G1 appearance is Siege, because the arm cannon can be removed and he got all of the bells and whisles of a modern figure, plus he pretty much in scale with OP from the same line