In a very early issue, Loki erected an impenetrable barrier around Thor's hammer, preventing him from lifting it. The day was saved when Donald Blake tricked him into dropping his guard... with a cardboard cutout◊ of Thor.
Thor once defeated the Absorbing Man by turning him into air.
From the 70s: the Absorbing Man is giving Thor a really tough fight since he touched Mjölnir. Thor turns and runs into a store with Absorbing Man following him and cornering him. Thor has had enough fighting so he hands his hammer over which Absorbing Man takes gleefully and then decks Thor, only for his hand to get painfully squashed and then knocked out by one punch. The store they're in? A toy store and Absorbing Man had unwittingly absorbed the powers of a cheap cardboard Mjölnir.
When Beta Ray Bill knocks Thor's alter ego Donald Blake unconscious. Looking for the powerful weapon Thor used he finds only a stick. Whacking it against a his ship in anger and exclaiming the curse "Thunder and lightning!" he is surprised to find himself holding a magic hammer that lets him easily defeat some SHIELD agents. (Iss. 337)
Odin, facing down Mjölnir thrown by Beta Ray Thor so hard the air behind it is on fire, catches it in mid air. (Iss. 338)
After Agnar attacks Balder, he has to sit through a 5 page lecture by Volstagg (with Volstagg sitting on him) on why Baldur won't fight him back. He is finally let up and left with some parting words from Volstagg: "Surely if some harm came now to Balder and you were responsible, why I might even find it in my heart, so much larger than that of ordinary men, to forgive you. Why, even Thor or Fandral the Dashing might forgive you because they were once young and daring themselves. But Hogun the Grim? Hogun was never young. He would never forget ... or forgive!" (Iss. 340)
Baldur, willing to die to protect his oath not to kill, is goaded by Malekith and forced to kill a battallion of demons to fulfill a mission that could save billions of lives. He then proceeds to force Malekith to teleport away and beheads Loki.
Who then manages to make the scene even more awesome by getting up once Balder leaves and finding his head with all the concern of someone missing a sock.
Loki: "After all, the first thing a sorcerer of quality learns is to make himself as difficult to kill as possible."
Surtur, the ruler of the fiery realm of Muspelheim, destroys a galaxy because he needs the heat to forge a sword.
The forging of Twilight is a CMOA of its own. For an entire year, Simonson had one page per issue of the forging, with each strike producing a massive "DOOM!".
The final three-issue confrontation in Asgard where Thor, Odin and Loki fight Surtur to keep him from ending the world.
In the aftermath with Odin missing, some frost giants are spying and think it might be a good time to attack Asgard. Hela comes to claim Odin's spirit for Hel. After administering a vicious beating, Thor yells at her as she flees "Flee, Death! Flee and lick thy wounds, you who are not fit to utter my father's name! And know that Thor shall not be far behind!" The frost giants quickly reconsider their attack plans and opt for a long trip to the mountains.
Thor, under a love spell, walks in to find Loki sleeping with the object of his affections. She has him bow down but teases him too much and his rage offers him a moment of sanity. He throws his hammer up into space and holds Loki by the throat over the balcony until he will release Thor from the spell: "Look you, Loki, to the sky! For there soars the hammer of Thor and by royal Odin's decree, it must return to my hand. Nothing may bar its way! Not even the head of Loki!"
Loki once turned Thor into a frog. The story was played seriously, and even had heartwarming moments as Thor defended the Central Park frogs against an army of rats. With Loki about to seize the throne of Asgard, Thor had to lift Mjölnir in frog form to be able to stop him. With the rats closing in on him and his back about to break, Thor succeeded in lifting the hammer. The next issue's cover and title say it all.
Cover: What do you call a 6'6'' fighting-mad frog?
Thor leads an army of Asgardians into Hel to rescue mortal souls held there by Hela. He wrestles Hela for their souls and is winning when she smites him with the hand of glory, mangling his face and sapping the life from him. Hela tries to make him kiss her cape and he rips it from her, robbing her of her power. He forces her to abide by the bargain or he will rip the cape (which he barely has the strength left to do). He grows his beard to hide the scars. (Iss 361)
Hela curses Thor with brittle bones that won't heal and an inability to die. He proceeds to break his arm, some ribs and a hand but creates a suit of Asgardian steel that will hold his body together. He wakes up in Loki's castle and saves him from frost giants. They break in just as the armor materializes around him and don't recognize him so he has to explain himself: "MY sire was ruler of the GODS rash thurse! Odin was my father and the thunder and lightning are my birthright! They speak my name in whispers in the nurseries of thine icy home!"
The giants summon the world serpent (which encircles the entire Earth) who is destined to kill and be killed by Thor at the end of time. Some of the best dialog I have read in a comic ensues in Thor #379 as the world serpent appears in another guise as Fin Fang Foom (complete with underwear!) to find Thor and fails to recognize him due to the armor.
The time Thor hit a serpent the size of a small state so hard that it breaks every bone in both of their bodies. The explosion was so big the sound effect had seventeen Os.
To save the world, Thor unleashes his full power against the world-serpent, knowing it will break every bone in his body, forcing him to live in torment until Hela lets him die. Thor: "You are a mighty fighter, but in the end, you are only a selfish creature while heroes... heroes have an infinite capacity for stupidity! Thus are legends born!"
The entire issue with Thor versus Jormungandr, aside from the dialogue, is written as and in the style of classical Old Norse skaldic poetry. And it is amazing.
Nine steps the hero takes striding as a giant
The entire issue is done in splash pages. Also, did we mention that Jormungandr is the size of New Jersey? And Thor gets swallowed and gets free by flying out through his teeth?!
As giants are taking out their frustrations on the immobile form of Thor's armor filled with his undying jellied body, Loki summons the Destroyer, the ultimate weapon created by Odin to fight the Celestials, who has been a melted pile of slag in the Andes for years. After using the life force of one giant to kill all the others, the Destroyer tries to kill Thor but cannot because of Hela's curse. The Destroyer enters the spirit realm to claim this indestructible life force which will make him invincible, but fails to recognize the being as Thor, who had beaten the Destroyer there before. As the spirit Destroyer tries to run away and screams "NO!!!", spirit Thor grabs him and says that only one will leave alive. Back in the real world the Destroyer puts on Thor's cape, belt and head feathers, picks up Mjölnir and teleports away. (Iss 381)
To reiterate: The Destroyer's reaction when he finds out his foe is Thor is absolute terror.
Thor, in the Destroyer's body, lays waste to Hel with ease. (Iss 382)
Thor drops by for a friendly chat with Loki about all the trouble he caused Thor and Asgard lately. Thor nonchalantly breaks Loki's arm with Mjölnir as a reminder "Only Odin's forebearance was infinite!"
And then flies merrily off, musing about how visiting his brother always cheers him up, and he should do it more often.
All of the above moments from 337-382 comes from Walter Simonson's time on the comic. There's a reason many fans consider it not just the best run of Thor, but the best run of any title ever.
Simonson wrote, drew and inked the first two and a half years of the title, along with #380 (the aforementioned all double-page-spread issue). He would've drawn more had he not taken on other titles at the time. There were only two writer fill-ins during his tenure.
When Comic Book Resources ran a "Greatest Thor Stories Ever Told" contest, six of the winning choices were by Simonson... including the entire top five. The only other writer close to achieving such domination in one of those contests was Larry Hama, who took nine out of ten slots on the Greatest G.I. Joe Stories contest. Keep in mind that Hama has written about 75 percent of all G.I. Joe stories ever published, while Simonson's run was only about fifty issues in the title of one of Marvel's major characters.
In one of the earliest stories, Thor vs the Carbon Copy Man, Thor is against an alien that can change forms to anything. So said alien makes himself invisible, and whales on Thor with an iron fist. Thor, cunning bastard he is, makes rain, and finds his adversary. After knocking him out in one blow, Thor wraps him up in a metal net. And then throws him OUT OF THE SOLAR SYSTEM!
That line he gives to Ultron.
Ultron. We would have words with thee.
The Hammer And the Holocaust! (Thor 127, April 1966): Stripped of half his powers then beaten to a bloody pulp by Hercules, Thor still manages to single-handedly save Asgard from usurper Seidring The Merciless. As Thor collapses near death at the foot of the Odinsword (yes, it was that close), The Old Man finally admits: "Thou art the noblest Asgardian of all."
Three issues later, a newly recovered Thor takes down the entire frigging Netherworld in a battle for Hercules' soul. When Thor finally emerges victorious, the Son of Zeus proclaims him the greatest warrior he hath "e'er known," swearing friendship until his dying breath.
Meeting Iron Man again after Civil War and proceeding to curb stomp him before telling him the reason Tony's been able to take him on before was because he was holding back, and then lecturing him on just who he is, what that means and about the incidents in Civil War. It's worth mentioning that Iron Man initiated the confrontation and believed he was fully prepared to deal with him. Thor took him down with one hit.
Later on, at the very start of Invincible Iron Man, Thor and Iron Man meet at the funeral of a group of super-heroes. When they confront each other, Thor very lightly taps Iron Man's armor... and cracks it. This was the Extremis Armor, which at the time was arguably the strongest conventional armor Tony had ever fielded.
Journey Into Mystery #106 involves Mr. Hyde ambushing Thor after the thunder god saves a coliseum full of innocent people from him and the Cobra. Fed up with being jerked around by Hyde and disgusted by Hyde's threatening so many innocent bystanders, Thor decides to settle with him once and for all. Thor does so by deliberately dropping Mjölnir, saying that if he can't defeat Hyde within sixty seconds he doesn't deserve his powers. Thor then pulverizes Hyde in a vicious Curb-Stomp Battle, beating him down with his bare hands and leaving him unconscious for the police, all within less than a minute.
In the latest series of Thor books, the Thunder God himself is teaming up with his future Old Father self to face off and finally destroy the 'God Killer'. However...the main point of awesome recently is Thor's younger self, back in Viking Times: he manages to face Apocalypse of all people, survives...and...later beats him and mortally wounds him with his axe despite his father's wishes!
In Siege #2, Norman Osborn sends Daken and a team of H.A.M.M.E.R. soldiers into Braxton to find a battered and supposedly defenseless Thor. And they find him, and in one panel he blasts the H.A.M.M.E.R. soldiers and Daken, leaving Daken a severely burnt, smoking corpse before making a Badass Boast.
Thor: I will not run from you Osborn, nor your minions. I will not hide. I will defend my home, and the home of my father... with my very last breath.
The tragic, heroic death of Bill, born of Bills. He was a mortal fry cook who fell in love with Kelda, a goddess of light. Against all odds, he successfully wooed her, but when he learned that Doctor Doom and Loki were concocting a plan to dissect Asgardians, he tried to stop them with a sword despite having no experience wielding one. Bill was mortally wounded and died, but passed on the message that saved the people of Asgard. As a reward, he was taken to Valhalla—and when Kelda herself died later on, they reunited there.
The last words of Bill, Born of Bills. He doesn't care that he's going to be honored like a god after death. All he wants is for Balder to make sure to tell Kelda that even after the arguments they'd had recently over the fact that she's an Aesir and he's mortal, he still loves her.
One of the earlier Simonson issues involves the last viking trying to goad Thor into killing him. Thor is impressed and gives the viking some strength and a flying horse to help him against an attacking dragon. An old man approaches the viking and enchants his spear with good luck before the fight, the viking receives a mortal wound and loses his strength. He is determined to keep fighting so with the last of his strength he falls with his spear beneath him and finally wounds the dragon and giving Thor an opening to finish. He earned his place in Valhala that day.
Thor vs. Malakith in issue 347: Malekith's monster form cannot even touch Thor and is thrashed around for a page.
Roger is a badass normal Korean War vet who is not afraid to fight Dark Elves, hell hounds and nearly kills Malekith even when he can't see him and delays the eternal winter.
Once, Thor was sitting exhausted after a massive battle with a villain. An unnamed paramedic walks up to him and hands him Mjolnir before walking away. It takes a moment for Thor to realize the significance of this: he had just encountered someone worthy to wield Mjolnir. For clarification, of all of the Avengers, only two of their members have been worthy to wield the hammer, Thor himself and Captain America. The Real Heroes indeed.