Thor's a beast but nah...Even if we take into account Rune King Thor (Disassembled arc, gained Odinpower, sacrificed his eyes for even more power, instapwn'd Mangog, decapitated Loki, defeated Those Who Sit Above in Shadow by cutting a string thus ending the cycle of Ragnarok. Mind you, he didn't fight Surtur, he actually went to Surtur and gave him the ok to march upon Asgard), he still would face heavy competition from these guys:
Classic Odin: transported Earth's entire population across space
When the Infinity Watch along with Silver Surfer and Thanos brought Thor (inflicted with Warrior Madness) to Odin, Odin proceeded to one shot Silver Surfer and got the better of Thanos in the ensuing fight.
Archenemy: Destroyed Nightmare's realm, destroyed Mephisto's realm (Mephisto had to be rescued by Magik), destroyed Sutur's realm (Muspelheim). In fact Mephisto had to team up with Dormammu, Magik, and the other rulers of the Splinter Realms to confront the Archenemy.
Agamotto: Stalemated Galactus in his realm
Sise-Neg: banished Shuma Gorath, all-powerful
Dr. Strange: Armed with his talismans and relics, basically held his own against Adam Warlock with the Infinity Gauntlet
Insane Genis Vell: Destroyed the 616 universe. nuff said
Disassembled Scarlet Witch: nuff said
Squirrel Girl: no explanation needed
Dormammu: slept on like what above posted wrote earlier
I'll try to think of more
Ps...people sleep on Zeus, thinking he some goofy version of Odin lol. He recently beat the brakes off the Hulk like the Hulk owed him money..plus the classic thrashing he gave the Avengers
Pss..peeps also sleep on this guy's power: