Microsoft and Bungie's Halo franchise spans an entire galaxy's worth of war and conspiracy, but a significant chunk of the universe's lore follows around the central character of the main games: John-117, the Master Chief. As a member of the UNSC Navy's elite SPARTAN II program, Chief is a cybernetic super-soldier who not only proves to be a powerful warrior in battle, but perhaps the greatest hero humanity has ever known. Master Chief has been awarded with every UNSC service medallion except for the Prisoner of War for very good reason.
Being stronger, faster and more skilled with weaponry and combat than a normal human could possibly be, Master Chief has performed amazing feats time and time again while under the player's control, from destroying the galaxy-killing Halo rings to taking out massive Scarab tanks on-foot and blowing up a Covenant Armada with their own bomb. In the games alone, Master Chief is a force to be reckoned with, but in the Halo expanded lore, the Chief's list of feats is perhaps even more impressive than in the games.
According to mother of the SPARTANs Dr. Catherine Halsey -- and by extension her A.I. duplicate Cortana -- that John-117 was not necessarily the strongest, the fastest, or the smartest SPARTAN around, but he was the luckiest of any of them. Perhaps that luck extended to little John's genes, because even at the age of six, he was stronger, faster and smarter than the majority of children in his class. The idea that others could excel at certain attributes over John is actually rather terrifying.
Throughout his appropriately Spartan-like training detailed in The Fall of Reach, John-117 grew to become an excellent soldier. The program's experimentation augmented his body to reach the physique of an adult Olympic athlete at the age of 14 years old. During his training, he was able to defeat four ODSTs and capture a bunker guarded by MJOLNIR-wearing marines, all without wearing MJOLNIR armor himself.
Much like other young SPARTANs, John could sprint at 35 miles per hour, lift three times his own body weight and see in the dark. This was further augmented by the MJOLNIR Mark IV armor, which is so reactive and powerful that a normal human would be torn apart simply trying to move in it. It was while wearing this armor that he fought his early military career against the alien Covenant -- during which he would rack up a huge body count.
Alongside fellow his fellow SPARTANs in Blue Team, Chief opens The Fall of Reach slaying well over a thousand Grunts in the prologue alone. Not only does his team kill several with their assault rifles alone, but Chief's tactics allow him to lure the Grunts to be blown up by a hail of grenades rolling from the wall of a cliff. The battle climaxes with the destruction of a Banshee with an improvised mortar.
In Oblivion: A Master Chief Story, Chief and Blue Team were defending the planet Mesra from yet another Covenant invasion. During this time, they managed to destroy several Wraith tanks with diminishing resources. In the games proper, this is a difficult stunt to perform even with only two Wraiths facing the player, without a horde of Covenant around in-tow. Notable is the feat of pure strength involved: lifting a heavy Gauss cannon as a portable turret against said tanks, which is otherwise impossible in the games.
When he received the MJOLNIR Mark V armor he would use in Halo: Combat Evolved, Chief tested his upgraded power against a super fast fighter jet, deflecting almost all of the jet's automatic rounds. He breaks the bones of several ODST troopers, trying not to kill them. Most impressively, he deflects a Scorpion anti-tank missile that was homing in on him. What makes this particular training event noteworthy is that the overseer, Colonel Ackerman, was deliberately trying to kill John, but the Chief simply willed his way through the course purely to spite him.
While many of the astounding feats of strength and fortitude Chief performs in the Mark V can be accomplished by the player in Halo, there are several actions detailed in expanded lore that the player cannot replicate. Particularly, battling a huge Elite in hand-to-hand combat in space, sprinting at 66mph after taking a huge beating and surviving a frontal assault from a Hunter even after having his shields depleted by its fuel rod cannon are things that would instantly kill the player in the original game.
The only way a player could come close to matching Master Chief's strength in lore is by playing a Firefight mission on Easy mode while simultaneously being among the world's top players in Halo Major League Gaming. Even then, there are still plenty of techniques and abilities the player simply can't perform in gameplay alone. The Master Chief's legendary strength has transcended his own source material, and none of it has slowed down with age.