Attacking in Kid Icarus: Uprising is primarily handled with L. This works for both your melee and ranged attacks.
Continuous Fire: The basic ranged attack of most weapons in the game, continuous fire is used to maintain a stream of damage on an enemy. In multiplayer, a barrage of continuous fire can force players to dodge or sprint out of your line of fire. If they’re in a low health/low stamina situation, continuous fire can finish them off before they have a chance to react.
Charged Shots: When you have not fired your weapon for a short time, your reticle changes to reflect that you have a charged shot available. This is far more powerful than any individual rapid shot, and it’s a great way to open or finish any encounter with an enemy.
Melee Combat: When you get close enough to a target, and your reticle is lined up, it will change to reflect that you are aiming a melee strike at that enemy. Each weapon type has its own unique melee combination with its own special properties.
In multiplayer, it would be unwise to think of melee combat as a last resort to a bad situation. If anything, melee combat is just another way to create bad situations for other players. All melee combos end with a strike that sends your victim flying away from you. Use this to send your enemies into bottomless pits, lava flows, or even into ranged attacks set up by other players on your team.