How does pummeling work?

Solution 1:

From my experience, whenever I melee an opponent who doesn't have any shields, the melee always kills them. If you melee when they still have shields, then only their shields are removed (thus taking a max of two melee attacks to kill an opponent).

Edit: The Bungie Weekly Update for September 24 has more information about how melee attacks and headshots work in Halo Reach. The basic idea is the same: melee will destroy any remaining shields (and nothing else), while a melee to a shieldless opponent will kill him.

Solution 2:

Andy's correct, except in game modes where health has been modified.

For example, I believe SWAT modes double spartan health, so even though you do not have shields in SWAT, a single melee attack will still not kill an enemy at full health. There may be other game modes either now or in the future that change player health percentages, but I can't think of any.

Under any 'normal' game mode, any melee after shields have popped is a kill.

Solution 3:

If the opponent has 10% shields (just a rough guess but it has to be pretty low) the melee attack with anything will kill the opposing enemy.