Characters That Have Destroyed Thanos
Long before he started collecting Infinity Stones in the MCU and laid waste to the Avengers in Infinity War, comics readers were well aware that Thanos is undoubtedly one of the strongest beings in the Marvel Universe—a genius-level intellect who possesses superhuman strength, speed, and reflexes, in addition to being nigh invulnerable. Plus, being an Eternal of Titan grants Thanos practical immortality. He's a god, for all intents and purposes. On paper, Thanos sounds invincible, but he isn't. Although his massive power and unquenchable thirst for domination have made him a persistent thorn in the side of many heroes over a span of several decades, the Mad Titan is never quite as formidable as he'd like the rest of the Marvel Universe to believe. In fact, he's been defeated on more than one occasion, although he definitely usually gives (at least) as good as he gets. Let's run through some of the craziest ways heroes and villains have gotten the best of Thanos.
Drax the Destroyer
At the end of James Gunn's Guardians of the Galaxy, after the Guardians defeat Ronan the Accuser in battle, Drax the Destroyer tells Gamora that Ronan was only a pawn, and his real enemy is Thanos. They haven't had a ton of screentime together, so we're still waiting to see Drax attempt to get his revenge on Thanos in the MCU. If he does, then hopefully we'll see Drax destroy Thanos the same way he did in the comics: by punching a hole through his chest.
In Annihilation #4, during the Annihilation War crossover event, Thanos allies himself with the villain Annihilus, whose plan is to harness the Power Cosmic to destroy all life in the universe (including Thanos'). Upon discovering this information, Thanos attempts to free Galactus in order to get revenge on Annihilus, but before he can do so, Drax punches him through his chest, ripping out his heart in the process. While it's unlikely we'll see Thanos meet this grisly end in Avengers 4, perhaps it's something Marvel will keep in mind for a future Guardians of the Galaxy movie.
Adam Warlock
Not long after Thanos' initial defeat by Captain Marvel, the Avengers, and the supercomputer ISAAC, the Mad Titan aligns with Adam Warlock, along with Pip the Troll and his adoptive daughter Gamora, in fighting Magus and his intergalactic religious group, the Universal Church of Truth. Warlock later discovers that Magus is, in fact, his future self, one that was at some point corrupted by the Soul Gem (one of the six Infinity Gems, or Stones, as they're called in the Marvel Cinematic Universe). To prevent himself from succumbing to such a fate, Warlock travels into the near future and removes his future self's soul.
It's only later, when the Stranger attempts to steal Warlock's Soul Gem, that Warlock learns of the five other Infinity Gems. At this point, in Marvel Two-In-One Annual #2, Thanos concocts a plan to betray Warlock and seek out Mistress Death by stealing the power of the Soul Gem and combining it with the five other Infinity Gems to destroy the Earth's sun. Unfortunately for him, Warlock allies with Captain Marvel and the Avengers to destroy Thanos. In doing so, though, Thanos kills Warlock. However, shortly after that, Warlock materializes from the Soul Gem and uses its power to turn Thanos to stone.
Himself
Ever since Thanos' reveal in the mid-credits scene of The Avengers, the MCU has been leading up to a showdown between Earth's mightiest heroes and the Mad Titan—which we finally started to see in 2018 with Avengers: Infinity War, a conflict loosely based on Jim Starlin's famed Infinity Gauntlet story arc.
In Infinity Gauntlet, Thanos manages to acquire all six Infinity Stones and mounts them onto the Gauntlet, granting himself omnipotence and omniscience. By simply snapping his fingers, he wiped out half of the universe's population, including virtually half of the heroes on Earth.
Doctor Strange, Silver Surfer, and Adam Warlock concocted a plan to defeat Thanos with the help of Earth's remaining heroes. However, nothing in their power could stop the Mad Titan. In the end, Thanos was only defeated by willingly giving up the Infinity Gauntlet and temporarily becoming one with the universe—thus opening an opportunity for Warlock to put on the Gauntlet, and all the other heroes to attack.
Squirrel Girl
Squirrel Girl has been popping up in the news lately, with actresses like Anna Kendrick and Shannon Purser expressing interest in playing the character in the Marvel Cinematic Universe. Anthony and Joe Russo have even said that Kendrick playing Squirrel Girl is "perfect casting," which Edgar Wright agrees with. Wright went as far as to point out that several actors in his movie Scott Pilgrim vs. The World have gone on to play major superheroes, including Chris Evans as Captain America and Brie Larson as Captain Marvel.
It may be Kendrick's turn to play a superhero — even if it's not Squirrel Girl, who ended up being played by Milana Vayntrub in the New Warriors TV series — but if the character does end up coming to the big-screen MCU, then the Avengers just might have a chance at defeating Thanos. After all, Squirrel Girl has managed to take out some of the most powerful supervillains in the Marvel Universe all by her lonesome — merely by using her ability to communicate with squirrels. For instance, during the GLX-Mas Special one-shot in 2005, Squirrel Girl defeated Thanos with the help of her trusted squirrel, Tippy-Toe, thereby saving the entire Multiverse.
Thane
Early in Thanos' life, at the behest of Mistress Death, the Mad Titan killed his mother, wife, and children. Then he proceeded to slaughter millions of people across the universe, all in the hopes of persuading Death to become his bride. Years later, during the Infinity crossover event, readers discovered that during his travels, Thanos fathered an Inhuman/Eternal hybrid son named Thane.
Uncovering Thane's whereabouts becomes the impetus for Thanos' invasion of Earth. He begins by leading a charge against the Inhumans' home and sanctuary, Attilan. It's worth noting that Thanos doesn't just want to find Thane—he wants to kill him.
Later in the story arc, in Infinity #6, Thanos' lieutenant, Ebony Maw, realizes that Thane, whose Inhuman power is literally the power of death, could become more powerful than his father. He betrays Thanos by using a suit to contain and control Thane, thereby forcing him to encase Thanos in a limbo-like stasis known as "Living Death."
Zombified Hulk
In 2005, Marvel made their first attempt at a zombie story arc in the Ultimate Fantastic Four #21, dubbed "Crossover." The publisher must have liked the story, for later that year, they commissioned a Marvel Zombies limited series by The Walking Dead creator Robert Kirkman (fitting, eh?). The series was such a success that they ordered a sequel, titled Marvel Zombies 2, in 2007. More installments followed in 2008 and 2009, finally concluding with a fifth series, Marvel Zombies Return, at the end of that year.
The first issue of Marvel Zombies 2, set in the alternate reality of Earth-2149, features the remaining heroes and villains of Earth at the edge of the known universe, 40 years in the future. By this point, as zombies, they'd consumed all there was to consume in the entire universe, and their insatiable hunger only grew. A zombified Thanos made a sly remark that they would have more food if Hulk hadn't eaten so much more than everyone else. Of course, Hulk didn't approve of the Mad Titan's comment and responded by smashing his head into oblivion.
Himself (again)
After Thanos is turned to stone by Adam Warlock following his first bid at acquiring the six Infinity Gems, Mistress Death resurrects him in Silver Surfer #34. He almost immediately continues his pursuit of the Gems in The Thanos Quest arc—as well as his quest for omnipotence and universal domination, depicted in The Infinity Gauntlet limited series.
As previously mentioned, Thanos essentially allowed Nebula and the heroes of Earth to defeat him. In the follow-up series, Warlock and the Infinity Watch, the Living Tribunal directed Warlock to disperse the Infinity Gems so no one could ever find them and attempt to use the Gauntlet again.
Warlock formed the Infinity Watch, consisting of Drax, Gamora, Maxam, Moondragon, Pip the Troll, and Thanos, all tasked with protecting one Infinity Gem each. Together, they fought anyone who attempted to steal one of the Gems, including themselves. During the Infinity War crossover event, Thanos fights his evil doppelgänger and narrowly defeats him, only to go after Magus and Warlock in the Infinity Watch #10.
Death
The first issue of Thanos' 2016 ongoing solo series ended with the revelation that Thanos, though at the height of his power to all outward appearance, was dying.
The Mad Titan had no idea why, or how to reverse the progression of his illness. Desperate, he went to his father Mentor searching for answers. When Mentor had nothing to give him but well-deserved hate, Thanos murdered him with his bare hands.
In Thanos #6, the source of the villain's problems was finally revealed — Death itself or, more accurately, herself. Appearing much more attractive than the skull-faced hooded figure we're used to Thanos trying to woo, Marvel's personification of Death had given Thanos his debilitating illness to prepare him "for what comes next."
Of those who have the honor of defeating Thanos in physical combat, a healthy chunk came in the pages of Thanos after Death's illness took hold. First Thanos was still powerful, but weakened. Eventually he grew so fragile that any average jerk could smack him around. Considering it was her illness that made Thanos so utterly beatable, one might reasonably argue it was Death's victory every time.
Starfox
The final humiliation Thanos suffers during his illness and subsequent loss of power is at the hands of the last person most would expect — Starfox.
With Thane slaughtering whole worlds at Lady Death's behest, the group that originally formed in Thanos #2 to kill Thanos recruits their former target to help them defeat Thane. Thanos' plan is to travel to a place he sensed during Infinity Gauntlet – when he had all six Infinity stones — called the God Quarry. There, he tells his new allies, they will find three powerful witches who have the power to restore his might.
In Thanos #9, moments after arriving in the Quarry, Starfox foolishly tries to use his empathic powers on the witches to convince them to give Thanos what he needs. The witches suck the life force out of Starfox as punishment, changing him to an old, ugly man.
They restore him once he begs forgiveness and Thanos laughs at his humbled brother. Starfox — the guy who spent almost every page of Infinity Gauntlet imprisoned with his mouth literally erased from his face — lashes out and gives Thanos one final, well-deserved beatdown.