Thor is fully trained in asgardian combat styles. He wins.
Via headbut.
__________________ Quotes from Hia8:
"I claimed that the science is sometimes faulty."
"You don't understand. This is fiction. That means none of this stuff really happened."
"There is no writer to purposely ignore a character's natural ability just because it suits the story."
"in some cases because the writer knows that Character A will dominate Character B easily and refuses to allow this to happen for the sake of the story."
Thor absorbs Thanos' blasts, amps them a hundred-fold back at Thanos, immediately calls up the strongest cosmic storms he's summoned to keep him off-balance, and immediately follows that up with a quick Anti-Force blast and knocks him out.
If this sounds familiar to anyone, brownie points for you.
Thanos has the edge physically and is -on average- more powerful than Thor but he doesn't bring anything to the table that Thor can't handle. If by going all out Carver means Thor pulls out the less used abilities like the God Blast, charged hammer strikes, energy absorption etc. then Thor wins.
If not, the Odinson has a strong enough history against high class opponents that this being a great fight isn't even really debatable and I really could see it going either way. Unless this is a purely high end showings fight or something. I would like to see the end result of a Thor/Thanos confrontation if the Mad Titan had killed Sif or something in front of Thor.
I'm pretty sure this fight already happened in the comics, except Thor was even more powerful because he was amped by the power gem. Without the power gem, his performance would be a lot worse.