Why a single melee can kill you in Halo:

That's good but I thought that you just Break the nuclear reactor in the back with one punch. Than the suit does the rest.thats only from the back.

4823717 Matpat misses some important pieces of information. In Halo ODST, your melee attack does less damage because you are NOT an augmented powered-armor wearer. The augmented muscles, bones, and organs that he mentioned? Those bones are why a Spartan's sudden spasms don't break his bones and crush him. Those organs improve survivability in harsh environments. The muscles allow them extreme speed, which is then in turn augmented by Mjolnir's fast reaction times. Those muscles are far more strong than a normal humans, allowing more force to be put behind them. Multiplied by Mjolnir, that's a lot of power behind a hit.

The situations Matpat describes are Multiplayer situations, Spartan against Spartan. These Spartans are each hitting eachother with quite a lot of force mentioned above. Not to mention all of the various weapons they use (Bullets/Projectiles, Explosives, Guided Plasma, Lasers, Concentrated Light)

This does not change his conclusion very much, but what I've brought up does deserve mention.