Few characters can stand against him, with only a few being so brave and some being very foolish. While the MCU Hulk was not able to defeat Thanos, his comic book counterparts pose a better chance to make an even fight particularly if Thanos does not wield the Infinity Gauntlet.
Thanos Beat Hulk Because He Was A More Skilled Fighter
This physical power does show itself in Avengers: Infinity War's opening as Hulk has a moment where he does overpower Thanos, but the fight quickly goes in the other direction.
After Avengers: Infinity War, some people thought Hulk feared Thanos, but the real person he fears is one he can never truly defeat. In Avengers: Infinity War, the Hulk proved that he couldn't take on every threat in the Marvel Universe.
Thanos is one of the most deadly and celebrated villains of the Marvel Universe. It's incredibly tough for even the Incredible Hulk to stand against the supervillain. Be it the Marvel Comics or the Marvel Cinematic Universe, the Hulk has never defeated Thanos in a one to one hand combat.
In Marvel Comics' Ultimate Universe, it turns out that the bad guys created a pair of gauntlets with eight Infinity Gems. And the Hulk was powerful enough to wear both of them and beat his former teammates senseless!
The Hulk Wasn't a Scared Little Baby in 'Infinity War' After All. Pretty much every hero in the Marvel Cinematic Universe rallied to fight Thanos in Avengers: Infinity War (they lost, but that's not the point). One hero, though, was totally MIA after a brief bout with the Mad Titan at the start of the movie: the Hulk.
Fans know Spider-Man is strong, but Marvel confirms Peter Parker has the strength to not only survive a Hulk attack, but take him down too.
While the MCU Hulk was not able to defeat Thanos, his comic book counterparts pose a better chance to make an even fight particularly if Thanos does not wield the Infinity Gauntlet. These two titans in the Marvel Universe seem destined to do battle in some form or another.
The final verdict. It would be a very long fight since the Hulk is incredibly hard to kill, thanks to his super-tough skin. But, in the end, Doomsday would be the winner due to his never-ending strength and endurance.
As per the user, the director of Avengers confirmed that Thanos was most scared of Iron Man. “Not because of his strength, not because of his power, not because of his power, but because of his suit,” he added.
Bruce Banner's deepest fear since becoming the Hulk is losing control of his emotions, which has been evident in his transformation into his bloodthirsty alter-ego, Kluh, in the AXIS storyline. Kluh's extreme ferocity even alarmed the Hulk himself, a testament to the danger he poses.
The theory posits Ego, Odin, and The Ancient One as three of Thanos' greatest fears, and he waited until all of them were dead to make his move.
So basically, Bruce Banner was unable to bring out the Hulk in Infinity War because he's been a lot happier/content lately than he was when he met the Avengers.
Following the battle against the Avengers, all of Hulk's former teammates were either dead or captured. Hulk was met with the same fate as Thanos captured him beneath his own palace, turned him into a servant, and referred to him as a dog.
So, there you have it. Thanos beats Hulk every time, with or without the Infinity Gauntlet. But World Breaker Hulk defeats Thanos. However, Thanos could beat the Hulk if he had the Gauntlet (He could wipe out the Universe).
Blonsky sought out and battled the Hulk to prove his superiority. Betty Ross called him an “abomination,” and Blonsky approved of that descriptor enough to take it as his name. The Abomination soundly defeated the Hulk in their first encounter, leaving him near death.
Thanos didn't lift Mjolnir, Captain America did
With Mjolnir's worthiness enchantment resulted in Thor being able to lift the hammer only if he is considered to be worthy, but likewise, the enchantment is not discriminatory in nature, and anyone who is deemed worthy is able to lift the hammer.
Before he can defeat him, the Immortal Hulk is stopped by the Savage Hulk, who is being emotionally manipulated by the Leader. The Immortal Hulk is beheaded by a monstrous Leader and his heart is ripped out. His corpse, alongside Banner, is taken to the Below-Place by the Leader.
He can lift a commercial airplane – which weighs around 100 tons – when he is at his calmest; that's no problem for him. But the angrier he gets the stronger he gets, and if the Hulk is really pissed, then he can lift anything, including mountains, or even planets!
Weakness: RAGE
While Hulk's rage makes him almost completely invulnerable and the strongest being in the entire universe, it also is a huge weakness. The increase of his power when in rage mode is massive. However, at the same time, he also loses almost all his intelligence when he grows angrier.
Horrified by what he could become, Hulk created an unconscious failsafe in his psyche that caused his body to revert to a powerless Bruce Banner whenever he got too angry. This also caused the Savage Green Hulk's mind to re-emerge in Banner's body, who couldn't understand why he was so weak.
The Avengers found that a certain lullaby, typically said by the Black Widow, was able to calm the Hulk and help him revert back to Banner, when the Hulk's strength was no longer needed.
The Hulk has been called the strongest Avenger given his unparalleled, planet-shattering strength, but within the 2099 future of Marvel and DC's crossover universe, the Hulk would be considered the weakest Avenger (for one specific reason).
Why was Hulk so weak in Infinity war? Because the writters wanted to Show all the version of Hulk in Avengers series,Marvel took that step and showed Hulk weak in Infinity war so that the final versionof Hulk that is professor Hulk could have been shown.