The player has acquired at least one weapon upgrade

Upgrade one of your guns, the pistol, shotgun, machine gun, chemical thrower, grenade launcher, or the crossbow. There are two upgrades available for each gun, so getting one upgrade for any of them will give you this trophy. The most likely point youll get this is at the end of the Neptunes Bounty level. After the fight with Peach Wilkins, youll have to find the submarine bay. On the way to this, there will be a Power to the People station where you can upgrade a weapon.