Introduction
Putrefy allows you to poison a creature when you deal Necrotic damage to them without a save. That’s a fantastic debuff, but the usage limitation means you won’t get to use it very often.
As great as Poisoned is, once per rest simply isn’t enough to justify this feat unless you have some other ability that requires an enemy to be Poisoned.
Ability Score Increase
Anything! Perfect. Necrotic damage usually comes from spellcasters, but there are several ways for martial characters to deal necrotic damage, so almost anyone can use this feat to good effect.
Necrosis
This is really good, but the usage limitation is very restrictive. Poisoned with no save is great debuff for enemies that rely on attack rolls, which might protect your party well enough to turn a fight in your favor.