This didn't work out so well in Vs, so maybe some Transformers fans will have an opinion.
Personally, I'm having a hard time deciding what's more impressive: Galvatron kicking Piranacon's rear with his bare hands and taking on a combined Autobot/Decepticon army, and one shotting the likes of Scorponok (Who could beat up Shockwave, who in turn can match Megatron), and Centurian (From "In the National Interest". Took Megatrons best shots, and looked generally impressive.), in addition to tanking Megatrons fusion cannon..
Or, Six Shot getting up after being smooshed like an ant, and than surviving getting stepped on by METROPLEX.
Galvatron has more impressive overall feats, and more varied feats, but SS survived Metroplex, man!
Well, in all honesty, while tanking a trample attack from Metroplex is impressive indeed (The guy has a footpat at least the size of a damn city block).... Oneshotting a being at least equally as big in Scorponok (Possibly bigger, since Fort Max is supposedly bigger than Metroplex, and Scorponok is as big as him) is even more impressive.
Comic book version of Fort Max and Scorponok aren't anywhere near as big as the cartoon versions though.. That goes for both Marvel and IDW. Metroplex is about as ridiculously large though (And in Marvel, he was tanking quintesson war ship and swatting them out of the sky with his bare hands! O_O )
Basically, Scorponok has always been only a little bigger than Shockwave or Megatron, and about as powerful. In Marvel, Scorponok was barely edging out Shockwave in a fight, and in IDW Shockwave edged out Scorponok (Scorponok was said to have 60% faster reflex's thanks to the Headmaster process, but the human component possessed fear, which Shockwave used to his advantage by fearlessly avoiding each attack by inches, to the point of them scraping along his armor, while Scorponok was practically dodging out of the way and leaving himself open...)
Thinking about it, I think Galvatron has the more impressive overall feats. IDW Optimus Prime was able to more or less hold his own with Six Shot, even if he couldn't do any damage, while Marvel Powermaster Optimus Prime was having a hard time with a hallucinating Galvatron that had half his face blown off by some experimental weapon...
Hmm, I may be overstepping my bounds, but I honestly think Fort Max And scorponok should be about the same size as Metroplex and trypticon, since all 4 of them have city based alt modes and battle station/starship alternates.