Marvel confirms a team that could finally kill Thanos
One comic proves that the Guardians of the Galaxy and the Galactic Council will be more than just a match for Thanos the Mad Titan.

Thanos has long been one of the most ferocious foes in the MCU, often a threat to the universe as a whole, but the hypothetical question suggests that there is one team that can take him up and win: the Guardians of the Galaxy, along with some key allies.
Since the debut of Jim Starling and Mike Friedrich in Iron Man #55, Thanos' presence and threat has only grown. In Jim Starlin and George Perez's Infinity Gauntlet storyline (loosely adapted by the MCU as Avengers: Infinity War and Avengers: Endgame) Thanos managed to assemble six Infinity Gems and wipe out half of all life in the universe. More recently, in Dan Abnett, Andy Lanning, and Miguel Sepulveda's The Thanos Imperative, Star-Lord and Nova believe that Thanos poses such a threat to the universe that they try to sacrifice themselves in an attempt to keep him trapped in the Cancerverse (all three both have gotten better since then). Time and time again, Thanos has faced massive combinations of heroes, only to be temporarily defeated by them, including at the end of Jonathan Hickman's Infinity event, where the best the Mightiest Man on Earth can do is trap him in a piece A substance similar to amber, and the whole universe thinks he is dead.
In what if? Infinity: Guardians of the Galaxy #1 with Joshua Williamson and Jason Copeland, readers get to see an alternate ending to these events. While in Marvel's mainstream continuity Thanos was eventually unleashed and took part in the events leading up to 2015's Secret Wars, here Guardians of the Galaxy finds him surviving and on Earth. The Guardians (Star-Lord, Gamora, Rocket, Groot, and Drax) decided to take matters into their own hands, trying to infiltrate the Illuminati, take over Tony Stark's armor and free Thanos. At this point they join the Galactic Council, they're "tired of his *#@$", and the two combined teams manage to destroy Thanos (if the Rockets are to be believed, they'll do it easily).
The Rule-Breakers And The Rule-Makers Are An Unbeatable Combo

The Galactic Council doesn't get their hands dirty very often, and for good reason. Consisting of Shi'Ar Majestor Gladiator, Annihilus of the Negative Zone, Brood Queen, Kree Supreme Intelligence and Super-Skrull, the group consists of Cosmic Mighty and Galactic Emperor. Each of them can (and most of them were) the main antagonist of a major event, and it is It's only fitting that they join forces to end, once and for all, a major shared threat to the universe. The sheer level of power they display clearly shows why parliaments do not often intervene directly - it is difficult to develop a credible opponent strong enough to challenge them.
While the Avengers are Earth's Mightiest Heroes, this issue reminds readers that the rest of the universe can provide stronger champions in times of need, and that the leaders of the major cosmic empires have earned their place. When the unpredictable ingenuity of the Guardians of the Galaxy combined with the unstoppable raw power of the Galactic Council, it seemed like even the Mad Titan would disappear in an instant.