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https://psnprofiles.com/?psnId=mrrj46 and
https://psnprofiles.com/VanqishdTo learn a weapon ability, a weapon's proficiency must reach 100% weapon's exclusive ability. This bar can be seen on the weapon menu.
To increase weapon proficiency, simply use the weapon-specific ability in combat. To do so, check which ability in particular the weapon you're carrying has, and once in combat press Cross > Abilities > and use the specific ability. Each ability "levels up" differently, but it is at least 10% per ability usage. Using an ability multiple times in the same combat to increase its proficiency rank is possible.
Below is a list of all the weapons available in the game and how to find them.
Cloud
Buster Sword – Focused Thrust
Default weapon.
Iron Blade – Triple Slash
Will be obtained in Chapter 3 as part of the story.
Nail Bat – Disorder
It is obtainable in Chapter 8 as a reward for the side-quest "Kids on Patrol".
Hardedge – Infinity’s End
Purchasable in Chapter 9 from the Weapon Shop Vendor (Wall Market).
Mythril Saber – Blade Burst
Purchasable in Chapter 14 from the Weapon Shop Vendor (Wall Market).
Twin Stinger – Counterstance
It is obtainable from a purple chest in Chapter 17 after Red XIII helps you cross some pods and defeat some enemies. It is next to a staircase and in plain sight, hard to miss.
Tifa
Leather Gloves – Divekick
Default weapon.
Metal Knuckles – Overpower
Will be obtained in Chapter 5 as part of the story.
Sonic Strikers – Focused Strike
It is obtainable from a purple chest in Chapter 7 in simple sight (Mako Reactor 5 - B5 Connecting Passageway).
Feathered Gloves – Starshower
It is obtainable from a purple chest in Chapter 10 from the area where water has been drained (Aqueduct 1).
Mythril Claws – Chi Trap
Will be obtained in Chapter 13 as part of the story.
Purple Pain – True Strike
This is one tricky weapon to get. In Chapter 16, you will play as Tifa and try to reach reception in the lobby of Shinra Tower. At some point, you will fall. To get back up you'll need to climb on top of a car and then proceed up a ladder. However, DO NOT climb the ladder, instead head for the bars to the right and you will reach a purple chest containing the weapon.
Barret
Gatling Gun – Focused Shot
Default weapon.
Light Machine Gun – Lifesaver
Will be obtained in Chapter 6 as part of the story.
Big Bertha – Maximum Fury
Purchasable in Chapter 13 from the Weapon Shop Vendor (Evergreen Park, the playground southeast of Wall Market). You can also purchase this from the same shop in Chapter 14.
Steel Pincers – Charging Uppercut
Purchasable in Chapter 14 from the Moogle Emporium.
Wrecking Ball – Smackdown
It is obtainable in Chapter 14 as a reward from the side-quest "Subterranean Menace",
EKG Cannon – Point Blank
It is obtainable in Chapter 16. After talking to the Mayor, head back outside and talk to "Hart". He will ask for 10,000 gil and give this weapon as a reward.
Aerith
Guard Stick – Arcane Ward
Default weapon.
Silver Staff – Sorcerous Storm
Purchasable in Chapter 8 from the Moogle Emporium. You can purchase it in later chapters as well (such as Chapter 14).
Arcane Scepter – Fleeting Familiar
It is obtainable in Chapter 9 as a reward from the side-quests "A Dynamite Body" or "Shears' Counterattack" - depending on if you do Set 1 or Set 2 of quests.
Mythril Rod – Ray of Judgment
It is obtainable from a purple chest in Chapter 11 not much ahead from the starting point. Right at the start, there's a bench and vending machine, the chest is on the other side of the fence. Backtrack all corners and you will see it, it's in the room on the other side of where the starting bench & vending machines are.
Bladed Staff – Lustrous Shield
Easily the trickiest weapon to obtain in the game. You must use "Steal" in Chapter 11 boss Eligor to obtain this weapon. You will fail several times to steal the item, but keep trying. You must equip the Steal Materia before the combat - but don't worry, at any time you can exit the Eligor combat and you will be sent back a few steps before the combat starts, giving you time to change your equipment. You can only use the steal ability by having the Steal Materia attached, which you can buy from Chadley after finishing Battle Intel Report 7. You can always go back via chapter select and get this after finishing the game.
Reinforced Staff – ATB Ward
This is obtainable from a purple chest in Chapter 17. It is at the very beginning and in plain sight, it will be hard to miss.