In Max Payne 3 for the PS3 and Xbox 360, you can melee someone in multiplayer and it’s essentially an instant kill if you can pull it off in time.
In multiplayer, melee is only available as an action. Once you are within melee range, you will see a button prompt come up on the screen, which will be Triangle on PS3 or Y on Xbox 360. If you can mash it before the other player destroys you, then they die and probably scream about how cheap your kill was.
Yes it may be cheap to make a melee an instant kill, but look at all the games out there that have instant kill melee.
If you don’t want to use it, then you don’t want to win, and if you don’t want to win then what the hell are you playing online for?