Sword of the Necromancer

I'm not 100% sure what weapons are required for this as I didn't complete the entire Weaponry when the achievement unlocked. The last weapon I acquired and used that got me the achievement was Bardiche. Nodamoe's Scriptures is not necessary for the achievement.
You can get weapons by opening chests on the dungeon floors. Since this game is a roguelite, the contents of a chest are completely RNG. You can get lucky and get this achievement soon or you will have to run the dungeon hoping for a weapon drop (like me).
If you have already finished the story and didn't get all weapons, I recommend you get an item with Dash Save attribute on an active slot, this way you can spam dash () endlessly (you can forge this attribute if you need to, I did it on a ring). Just run around the last floor looking for chests, don't even kill enemies unless you have to (like the rooms that close the doors and require killing everyone to proceed). The last floor has 4 or 5 chests. Once you open all of them, just press and choose to go back to the altar. This way you can keep exploring new generated last floor. Don't go to the boss room and kill the necromancer as this will start the dungeon floors again.

Here is my list on the Weaponry from when I got the achievement:
Sword of the Necromancer
Gladius
Sabre
Claymore
Lance
Halberd
Pike
Labrys
Throwing Axe
Bardiche
Longbow
Recurve
Grimoire G
Grimoire R
Grimoire F
???
???
???
Tama's Sword
???

Like other achievements in Sword of the Necromancer, "Weapon Master" will only unlock once you reach a boss room or go back to the altar (either by dying or choosing to go back through the menu).
I recommend you kill at least 2 monsters with any new weapon you find. You can keep track of the kills count by checking the Weaponry on the Library (the bookshelf on the left side of the Altar, below the stairs). The kills count is on top of the right page.

After completing the game you can go through the right door and choose the "dungeon builder".

While building the dungeon you can choose what's inside the chests like weapon types/armor etc. and you can choose what kind of monsters spawn with the cn_start button.

Just look at the libary what weapons and monsters are missing in your collection and use/revive them.