The DOOM games take place in a universe where a lone, very angry man regularly stops the forces of Hell from invading Earth through sheer force of will. Despite being, ostensibly, just a guy, the Doom Marine as he is sometimes known possesses a variety of superhuman abilities. Like being able to outrun a fucking car.
A thing we should clarify before we continue though is that the canon of the DOOM series is somewhat mess and that it’s not clear if the games chronicle the adventures of a single man or a series of men who’ve taken up the impossibly sweet mantle of The Doom Slayer.
However, at least according to the game Quake Champions (in which the Doom Slayer makes a cameo appearance), the Doom Marine from the 2016 reboot is absolutely the same guy from the original DOOM. With the obvious timeline discrepancies that this causes being explained away by saying that due to Hell shenanigans, the Doom Marine can travel through time and across realities as and when he feels like it if there are demons that need to be shot. The thing is, if this is true it means that the Doom Marine is arguably the most powerful mortal man in fiction.
You see, through the 2016 reboot of the series it is hinted at by in-game artefacts and lore that you, the protagonist, are some kind of demon who has been waging an endless war against the hordes of hell, because fuck them. The game also establishes that the Doom Marine is so powerful that nothing in Hell could stand up to his unrelenting rage and as a result, rather than kill him, they just dropped a building on him. In fact, throughout that game the Doom Marine is shown as being capable of channelling pure hell energy into his own body to enhance his already considerable strength and is strong enough outside of his iconic armor to crush a demon’s skull with his bare hands.
Although you’d assume that the stuff revealed in Quake Champions means this is no longer canon that’s not exactly the case and it’s entirely possible that the Doom Marine is in fact just an ordinary man and that Hell’s forces simply assumed he was a demon due to how effortlessly he tears them apart and built up the legend around him. With the fact the Doom Marine has been fighting for eons without succumbing to age being explained away by time passing more slowly in hell or some shit.
What makes this amusing though is that if these two characters are one in the same, it means that the Doom Marine can run faster than a car. How do we know this? Well, enterprising fans of the first game have calculated that the Doom Marine in the first game can run at speeds close to 50 mph, while carrying hundreds of pounds of equipment forever.
Why the Doom Marine never tires or slows despite being human is never explained, though a popular fan theory is that he is somehow able to channel the ambient energy of Hell through his suit or body thanks to deal with some powerful demon who was also sick of Hell’s shit. However we personally prefer the other fan theory that the Doom Marine is just that fucking pissed he refuses to die. Why is he so pissed you ask? Well it is established in the game Ultimate DOOM that the Doom Marine’s sole motivation for returning to hell to punch every demon to death is that his beloved pet rabbit, Daisy, was killed when they invaded Earth.
Meaning yes, it is very possible that the entire reason Hell spends almost every DOOM game getting its shit wrecked by an unkillable, dimension-hopping badass is because they killed his pet rabbit.