Greatsword of Bloodweep (5e Equipment)
From D&D Wiki
Weapon (greatsword), very rare (requires attunement)
Get an order of paladins belonging to oath of the ancient to chase murder hobos and chain them to this to prevent friendly fire or add it to whatever weapon the character in question can wield properly and it will solve all your problems.
This weapon has a humanoid image carved into its body; while attuned to a person, the image cries blood in a gruesome display of the horrors committed by the owner.
Sure Strike. As an action, you may deal a single, devastating blow as this weapon homes into the enemy's weak spots. You automatically hit the target you were aiming for with this weapon if they are within range. This consumes one of the items charges, and it has a maximum of 3.
Allied Protection. Whenever you willingly damage an allied npc or pc, you must also make a DC 10 + the damage dealt Constitution saving throw. If you succeed on the save, you take half the damage you dealt to your ally; failure means you take double that damage, and acquire a fatigue point that can't be removed through the conventional means. Also, when you attack a friendly target, the attack automatically spends one of the item's charge, if any; when this happens, the target gains resistance to the damage.
Daily at dawn, if you have completed the day without attacking an ally, you remove 1 fatigue point, whatever its source, you regain one of the item's charges, and the item gains a cumulative +1 bonus to attack and damage rolls, up until it reaches +3.
Cursed: Once this item binds with the character, the owner can no longer enter combat of any form without using this weapon. It also cant be dropped or given away, as the owner will jealously guard it with its life. The curse can only be removed through the wish spell or if the remove curse spell is cast at 7th level or higher. The curse is also lifted automatically when the character spends a year and a day without attacking allies; when this happens, the image of the sword stops crying blood and assumes a content expression.
Additionally, once the curse is lifted, the item permanently receives the +3 bonus to attack and damage rolls, and recharges its active ability and all expended charges daily at dawn.