Korath explicitly described Thanos as the most powerful being in the universe in the MCU, but that's far from being the case in the comic books – but non-comic-reading casual cinema-goers certainly won't know that.
So, if you don't know the villain known as the Mad Titan too well, you might be surprised to learn that there are beings far more powerful than him in the comic books.
You don't even have to look to the truly cosmic or abstract entities (the likes of the Living Tribunal, Galactus, the Beyonder or the One Above All, for example) to find characters capable of beating him down – and this article will demonstrate that.
Here are five fellow Marvel characters who could defeat Thanos (this is assuming a straight-up fight with no prep or power-ups for either character).
Odin is at the absolute pinnacle of the power levels in Marvel Comics that fall just beneath the abstract cosmic entities that start off with characters like Galactus and, ultimately, reach likes of the One Above All. He has been portrayed by Anthony Hopkins in the Marvel Cinematic Universe, though that version has not yet demonstrated close to the levels of power of his comic book counterpart.
The Skyfather – which is considered to be a specific tier of power in Marvel, just above the level of Thanos – is proven as being capable of defeating the Mad Titan in battle. Although Thanos refused to give up in the battle (which is specifically depicted in the image below), the fact is that Odin was shrugging his attacks off with ease, while Thanos was notably looking worse for wear.
Moreover, Thanos was prepared for the battle, had the Silver Surfer helping him, and was going all-out, while Odin was being casual and merciful to say the least.
Odin is more durable and stronger than Thanos and, as a mere side effect of his battles (collateral damage, essentially) entire galaxies can be destroyed (something which happened in his fight with Seth, for example).
Through command of the powerful Odin Force, the lord of Asgard is capable of all kinds of crazy abilities – such as energy manipulation of a superior level to Thanos, the erection of forcefields, the casting of illusions and telepathy.