Greatsword
Greatswords are simple, decent damaging weapons that slightly slow the wielder down in combat.
Greatswords have 2 more damage than their sword equivalents, and an attack speed of 1.3, making them somewhat slower than swords. They also reduce movement speed by 15% when held, so dodging attacks may be difficult.
Greatswords can be crafted with the shown recipe, with the material of choice in the place of iron.
Iron greatswords can be found in Cellar vaults and can be wielded by Zombies, and diamond greatswords can be found in Cellar and Trial Chamber vaults.
Greatswords can be repaired at an anvil using their base material, like any vanilla tool.
As with all Valiance items, when upgraded with Netherite, greatswords may seem to not be changed in the smithing table output, but will once entering the inventory. (This issue cannot currently be fixed but will be in the future.)
Greatswords do not have very major downsides, since they only apply when being held, and do not cause the player much harm but rather simply slower fights. Because of this, it is quite reliable to have a diverse set of Protection-adjascent enchantments, ideally a different one on each armor piece.
A damage and speed-based Totem of Irregularity seems optimal, with a downside of either armor or max health, being best.