Corruption Domain

Masters of manipulating life energy to serve their purpose, Corruption Domain Clerics could Use their life corrupting magic to boost their allies,  twist the positive nature of clerical magic using it to cause great harm to their enemies, as well as using negative life energy to heal or ward off the undead. Corruptionl Domain clerics may seem evil at face value (and many tend to be) but the more pragmatic practicioners of the art would argue that their ways of manipulating traditional healing spells to harm life instead of bolstering it is just a minor creative difference from their life cleric counterparts. Even if they harbor no evil intentions corruption Domain practicioners have a hard time building temples or shrines in most cities and tend to have places of faith in more remote areas far from scrutiny. God's who grant access to this domain include, Kelemvor, Loviator, The Raven Queen, Urogalan, Myrkul,  or Jergal

Negative Manipulation

At first level, You have learned how to more reliably unleash your necrotic spells and learned to mold certain types of magic into negative energy.  When you deal necrotic damage to an enemy, you can reroll a number of damage dice up to your wisdom modifier (minimum 1), you must use the new rolls. This feature can be used a number of times equal to your proficiency modifier. You regain all expended uses after a long rest. In addition, any time you cast a spell that deals raidiant or force damage to an enemy, you can change the damage type to necrotic instead.

Heal or Harm

At first level, You have learned to make your healing spells more versatile, giving aid to your allies and harm to your foes. Whenever you cast a healing spell from the Evocation or Abjuration schools using a spell slot of 1st or higher but no higher then 5th level, you can choose to target an enemy and deal damage based on the number rolled instead of the normal healing done. This damage is necrotic damage and requires no saving throw to fail or spell attack to hit as long as the other requirements of the spell are met . 

Don't be afraid to be creative when describing the altered versions of healing spells causing pain and suffering on your enemies, you can even give them new names for flavor purposes!

For example; Healing Word can be Painful Word. Cure Wounds can Create Wounds. Aid can be Hinder, etc. 

Channel Divinity: Aura of Undeath

At 2nd level, the cleric can use channel divinity to radiate an aura of undeath, protecting you and your allies from undead, although less so against more intelligent undead creatures.

As an action the cleric raises their holy symbol and creates a 20 ft aura of undeath centered on you. Undead with an intelligence of 9 or less ignore the cleric completely for the duration as they consider you one of them. In addition any undead with an intelligence of 9 or lower that makes an attack within the aura on an ally who is also within the aura has disadvatage on the attack roll. An undead creature with an intelligence of 10 or above has disadvantage on attacks against the cleric as along as the aura is active and the undead is within the aura when making the attack. A undead with an intelligence of 10 or higher can attack your allies normally.  This aura lasts for 1 hour or until the until the cleric uses a free action to end it

Power to the Damned

Starting at 6th level, Your healing even extends to even the undead, and your animated summons can help you drain lifeforce from victims. You always have the animate dead spell prepared, not counting against your number of spells prepared. You can now also use healing spells on undead creatures that previously did not allow for it. In addition, any time an undead you created kills a creature within 90 feet of you that you can see, you can use your reaction to steal a portion of the victim's soul and heal 2d8 plus your wisdom modifier. if any healing goes above your maximum hitpoints when you heal this way, the remainder is gained in temporary hitpoints.

Potent Spellcasting

Starting at 8th level, you add your Wisdom modifier to the damage you deal with any cleric cantrip.

Chain of Joy or Misery

At 17th level, you bind yourself to either friend or foe giving extra healing to allies or pain to your enemies.  As a bonus action you can choose either a number of allies or a number of enemies within 120 feet of you that you can see (the number of alllies or enemies you can choose is equal to your wisdom modifier). If you choose allies, a radiant spectral chain ties willing allies together, for 1 minute or until you go unconscious. Any healing that affects one ally who is chained recieves, the other members who are chained heal for half that amount). If you choose enemies, a dark spectral obsidian chain lashes out and attempts to latch to your enemies . Each enemy chosen must make a wisdom saving throw (using your spell save DC). On a failure the creature is bound to the cleric for the one minute duration, and any time the cleric takes damage from one of the chained enemies all of the chained enemies take necrotic damage equal to half the damage recieved by the cleric .These chains last for one minute or untill dismissed as a bous action and cannot be destroyed by any means short of a wish spell. This feature can be used once per long rest.

 (For Clarification, any healing recieved by a spell like mass cure wounds would not heal a person chained more then the original amount rolled.)