Teeth on Teeth and Claw on Claw, yes nothing can pierce his hide but a black arrow.
Smaug's hide resisted a dip in melted gold..no suprise, he loves gold, he prolly drank it as well.
Forum Logic Goku>Wolverine Claws>Smaug
As we proved that the un killable wolverine can die from Goku, Adamentium claws cut through Smaug hide like butter through a hot knife, but fails to cut Goku as seen in Trunks SS1 with the legendary sword blocked by Goku's finger.
Dragon on Dragon Smaug will win because of his logic and his hide
More advanced forms or weapons or strength feats need to be put to the test
As seen in the movie as the trolls are trolling him in the dungeons. His head getting smashed in, rocks falling on him, blunt force trauma affects him greatly but was not shown to kill him thus far.
The explosives they used had little effect other then to prolly get a scratch out behind his ear..
Higher forms of energy and extreme blunt for trauma will affect his internals and he will fall because of this..
Yes there is only one way to kill Smaug dragon to dragon, Human to Human.
Goku is an alien and a far far advanced creature, his strength behind his punches will bash his brains
Energy Projection heat is higher temp then the melted gold which seemed to piss him off greatly..As a Kamamhamaha can destroy the earth..
Goku wins