Torturer

You relish in utilizing techniques that attack in more subtle, underhanded ways; poisons, bleeds and curses are your main tools; you excel in either gradually draining your opponents, or destroying them when they least expect to die. Some torturers relish in the suffering of others, while others use the pain as a means to some evil end. Extracting information has never been easy 

Poisoner's Proficiency

When you choose this archetype at 3rd level, you gain proficiency with the the poisoner’s kit. You have a poison DC, which you can apply to any poisons you might use, which is calculated using 8+prof+dex+charisma. Also, when you make an attack roll with a light melee weapon that has poison applied onto it, that poison's effects apply at the beginning of their turn instead of immediately. At the end of their turn, they may make a saving throw against the poison again (whatever save it asks for. Auto success if a poison does not ask for a save), but they can only attempt to resist the effects of one poison at a time this way.

Exsanguinate

Starting at 3rd level, you are at your deadliest when you are able to strike at the flesh of your targets. When you apply your sneak attack damage dice to a creature, you also begin to Bleed them. A bleeding creature takes half your sneak attack die again at the start of their turn. This effect can stack a number of times equal to your proficiency bonus, deals no damage to constructs, and deals double the amount of dice to unarmored creatures. The condition(s) ends when a creature succeeds on a medicine check with a DC equal to your poisoner save as an action on that creature while within five feet of it, or when they receive a larger amount of healing than your poisoner save.

Draining Curse

Starting at 9th level, you learn to wield curses in addition to bleeds and poisons to increase your potential for pain, even towards those without biological substance. When you hit a creature with a light melee weapon without applying any poisons to them, you may activate a curse. The curse lasts an amount of rounds equal to half your charisma modifier; rounded down.

Crippling Curse: While cursed, your movement speed is halved, and you can make one less attack than usual on your turn if you take the attack or multiattack action (Min 1).

Cancerous Curse: When this curse is applied, nothing happens. Every time a creature with this curse fails a saving throw, it multiplies itself; doubling the amount of itself on the target. At the end of a creature's turn, if it has 5 or more cancerous curses, 5 are expended, and that creature gains a level of exhaustion.

Torment Resistant

At 13th level, you learn the defensive skills to ward off others of your ilk; you feel no pain while being tortured, effects that would apply at the beginning of your turn fail to apply (Ex. Spirit Guardians), and you are immune to the poisoned condition. 

Sudden Demise

Starting at 17th level, you become a master at killing your opponents in a sudden shock. Your poisons deal double damage to targets at full health. In addition, if the minimum roll (combined) of your poisons, bleeds, curses, or other continuous, start of turn damage sources would bring a creature to 0 hit points, they die immediately instead. If a creature uses a legendary resistance while bleeding, it aggravates the wound, causing it to deal damage an additional time.

Finally, each of your methods for killing gains a special new tool

Mind Numbing Poison: You can make one vial of this special poison a day, which lasts 24 hours. when applied to a weapon, the next time you strike with it, the target must make a charisma saving throw, or lose a save or skill proficiency of your choice until they take a short or long rest. If you choose a proficiency they do not have, nothing happens.

Garrote: When you apply a bleed to an enemy for the first time, they are under the effects of the spell Silence, though it is not considered magical.

Torturous Curse: You gain a third curse option. While active, the next time the creature regains hit points, it instead loses that many.