The question of who is the strongest superhero has been asked ever since the first comic books were introduced. While this question might seem impossible to actually answer without relying heavily on personal bias, there is a definitive power level for the heroes of Earth within the Marvel universe.
To better answer this age-old question there are a number of parameters that need to be adhered to: first, the heroes that are to be considered must be Earth-side heroes and not cosmic in origin or strength (Luke Cage versus Silver Surfer is a terribly one-sided fight); secondly, no anti-heroes or villains such as Venom or Juggernaut; lastly, the heroes must be strong due primarily to their innate strength and not magical or technological means, excluding the likes of Doctor Strange and Iron Man.
Colossus Is One of Marvel's Strongest Mutants
The X-Men's resident strong man is much more than flashy metal skin. Colossus has proven himself to be immensely powerful with such feats as catching trains, lifting submarines out of the ocean, and even walking directly through War Machine's entire arsenal of weaponry.
His most impressive moments, however, include when he knocked out a Wendigo on his own, stood his ground against Gladiator, and traded blows with a rampaging Hulk. Colossus may not have won his battles against Gladiator and Hulk, but very few heroes would have been able to last as long as the brave X-Man did.
Luke Cage Is a Street-Level Powerhouse
A former convict turned hero-for-hire, Luke Cage is one of the last people a villain would want to tangle with on any day of the week. With nearly unbreakable skin and a strength level high enough to take on the likes of Doctor Doom and Proxima Midnight, Luke Cage has proven time and time again that he truly deserves the title of Power Man. His Netflix adaptation was no slouch, but in the comics, Luke can throw down with the best of them, even humbling Doctor Doom, of all people!
The Fantastic Four's Thing Is Always Top Tier in Terms of Strength
Despite being one-fourth of the Fantastic Four, The Thing has enough strength to hold his own against the mightiest of opponents. He was surpassed significantly by his main rival, The Incredible Hulk, over the years, but more recently, he humbled the Green Goliath with a decisive win. Despite any disparity in strength, of course, Ben Grimm never stays down.
The Thing’s rock-like skin and tremendous strength have also allowed him to take on not only Namor single-handedly, but even one of The Elders of the Universe, The Champion.
She-Hulk Is Low-Key the Strongest Hulk
Cousin to Bruce Banner, aka The Incredible Hulk, Jennifer Walters has some incredibly big shoes to fill when it comes to being a gamma-irradiated powerhouse. Luckily for her, She-Hulk has power in spades, and it's been said that her base-level strength actually exceeds her cousin's! Of course, his power is immeasurable when fueled by his rage, which unfortunately she doesn't beenfit from in the exact same way. That said, the recent power boost from which she just recovered was significantly more powerful.
No matter how you slice it, though, with enough power to punch through buildings, lift trucks, and create craters with single strikes, She-Hulk is more than most villains on Earth can handle.
Hercules Is the Prince of Power and May Soon Prove It in the MCU
A demigod born from Zeus and a human mother, Hercules has proven his godlike power time and time again. The Olympian has been able to battle the likes of Namor, Wonder Man, and Ares on his own, although nothing may have proven his strength more than when he was able to knock the Hulk down during his rampage in World War Hulk.
In a dark future where Hulk becomes the Maestro, it's shown that Herc actually used the moniker previously, and absolutely laid waste to the Hulk! He was only beaten by guile and noxious gasses, otherwise, Hulk would have been one dead green bean. Could this level of power be seen once he makes a jump to the MCU? Time will tell.
Captain Marvel Isn't Just Strong - She's Cosmic-Tier Strong
Carol Danvers has had a very long career as a superhero on Earth before she took on the name of Captain Marvel. Her vast arsenal of skills has enabled her to catch entire vehicles, tear pieces of spaceships apart, and pound many powerful villains into craters.
Captain Marvel has also been able to take down foes such as Nuclear Man and Blastaar and literally ripped Mac Gargan out of the Venom symbiote. In the MCU, she famously no-sold attack after attack by Thanos, and shot through his spaceship like a cannonball. No other Avenger can truly say that.
Wonder Man Is an Energy-Born Monster of Muscle
Simon Williams may be a movie star, but that doesn’t make his ion charged body any less powerful. Wonder Man has single-handedly defeated both Ultron and the Abomination, two of the most dangerous villains on Earth, and went head-to-head against Vision. Hercules has even stated that Wonder Man’s strength is comparable to that of Thor’s.
We've gotten a ton of teases of Simon in the MCU, but he's yet to have shown up just yet. When he does, though, expect him to humble even the toughest of opponents, be they friend or foe.
The Sentry Is Marvel's Disturbed Superman - and That's Dangerous
The Sentry is a force so powerful, there is hardly any other power on Earth that can stop him. Capable of withstanding nuclear blasts, The Sentry has performed a number of incredible feats, such as shattering Terrax’s axe and tearing both Carnage and Ares in half.
Perhaps The Sentry’s greatest display of strength came when he nearly ended the most powerful Hulk's rampage in World War Hulk. He didn't quite lock it down, but the Worldbreaker Hulk was another level entirely. e've said before that Sentry is probably TOO powerful for the MCU, but if Marvel really wants to shake things up, there's no better or stronger place to look than to him.
Thor Is Marvel's Go-To Hero When It Comes to Raw Power
The Mighty God of Thunder is a force of legend... for good reason. His strikes can shatter entire planets, he can shrug off force equal to that of the gravitational attraction of a neutron star, and he's survived direct energy attacks by the immensely powerful villains Terminus and Thanos.
The number of trials and tribulations that Thor has undergone are too many to count, but he has proven countless times his supreme level of strength. There is only one other force on Earth that can put the Odinson on the back foot but even then this contest of strength is won by mere inches.
Hulk Smashes Everyone
The Hulk is, without a shadow of a doubt, the single-most powerful hero on Earth. Holding entire planets together with his bare hands, shaking the entire multiverse with the force of his punches, and surviving the vacuum of space are just a few of the unbelievable feats performed by the Jade Giant. Having defeated opponents such as Gladiator, Armageddon, The Sentry, and Fin Fang Foom, Hulk is an incalculable force of raw power; the angrier he becomes the stronger he gets, granting him a near infinite level of power. While there are greater forces on the grand cosmic stage of the Marvel universe, there is no greater power on Earth than the Hulk, proving that at least planet side he truly is the strongest there is.
The MCU version of the Hulk is still immensely powerful, although not nearly as much so as his comic book counterpart. The Hulk has been shown as a supreme bruiser in fights against the Chitauri and Loki, and even against allies such as Iron Man and Thor. There's no question that the Hulk is an invaluable member of the Avengers in the MCU and was integral in defeating Thanos and his forces, but even then he wasn't shown to be the planet-splitting beast that he is in the comics. Hulk's ability to grow stronger the angrier he becomes hasn't been highlighted quite the way it has been in the comics. However, there is still plenty of time for the Hulk to unleash his full potential in the MCU during the current fourth phase of the cinematic universe.