The Broadsword is gotten from the Hall of Heroes once you've got 5 Chalices.
The sword has a percentage that goes down with use and from just being the active Weapon.
To get this Trophy all you have to do is go to the Gargoyle in the entryway of the Hall of Heroes that sells ammo and one of the options is to spend 100 gold to recharge the Sword do so and the trophy should Pop. (any of the Shop gargoyles should work though)