system
Given the following post, respond as if you're commenting on Reddit:
human
[Warhammer 40k] How physically capable is a single Space Marine?

Unarmored, as well as armoured. I just want to know how strong, fast, durable, skilled etc. a single *normal* Space Marine, from each Chapter, would be, compared to super soldiers from other universes ( say, Master Chief, Captain America, etc. )
gpt
Well, an average Astartes is 7.5-8 feet tall, and built more like a Football Linebacker in full padding than a normal human. They can run at a full Sprint for hours without tiring, eat basically any organic material, and survive injuries that would literally kill a human from shock (there's an old story of one taking a Krak Missile to the chest, and continuing to fight with half his chest cavity open for the world to see).

In terms of general feats, they can crush a human skull in a bare hand. That's about twice the total force a normal human can muster with BOTH hands. If the same applies across the board, they'd be about 3-4x stronger than the strongest human alive. 

Now, Captain America is hard to guage, because he's a comic book character... But he's supposed to be peak human potential. So, an Astartes would still be 3-4 times stronger than him. 

Master Chief is solidly super Hunan, but still struggles at some heavier weights, and is known to be vulnerable to comparable injury to a normal human (a 30 foot fall would still cause internal injuries, even if it didn't break bones). 

Speed wise, Master Chief is entirely outclassed. Astartes have millisecond reaction times, and can diflect low velocity roundse, subsonic with their bare hands. Chief needed AI assistance to deflect a missile moving a fraction of that.  Captain America is harder to judge, again, as hes shown to be able to dodge bullets, which is totally impossible if he is just Peak Potential. 

*** Its important to note, Cap and Chief are still human. One is enhanced to their physical peak, the other cybernetically and chemically enhanced. 

Astartes are no longer human. Their DNA has been rewritten, and they (often painfully, sometimes fatally) mutate into something else.