Who Would Win?

Mantis

Celestial Madonna, former adventuress, former bar-maid/prostitute/exotic dancer

Empathy, Precognition, Expert Martial Artist, Plant Communication, Pyrokinesis (celestial), Astral Projection

None (innate powers)

Guardians of the Galaxy, Avengers

Wanda Marya Maximoff

Avenger, mutant / nexus being

Flight, Telepathy, Telekinesis, Teleport, Psychic, Force Field, Blast Power, Healing, Magic, Invisibility, Fire Control, Psionic, Unarmed Combat, Weather Control, Divine Powers, Siphon Abilities, Necromancy, Electricity Control, Ice Control, Mesmerize, Astral Projection, Animation, Probability Manipulation, Precognition, Light Projection, Holographic Projection, Reality Manpulation, Levitation, Soul Absorption, Duplication, Emotion Control, Matter Absorption, Animal Control, Energy Shield, Time Travel, Siphon Lifeforce, Sense Death, Darkforce Manipulation, Illusion Casting, Wind Bursts, Earth Manipulation, Genetic Manipulation, Time Manipulation, Plant Control, Hypnosis, Water Control, Energy Absorption, Energy Manipulation, Cosmic Awareness, Willpower-Based Constructs

Darkhold (Book of the Damned) — mostly relies on innate chaos magic

A-Force, A-Next, Avengers, Avengers Unity Squad, Avengers West Coast, Brides of Set, Brotherhood of Evil Mutants, Darkhold Defenders, Defenders, Excalibur, Exiles, Force Works, Holy Guard, Horsemen of Apocalypse, House of Magnus, HYDRA, Hysteries, Lady Liberators, Nexus Beings, Romani, Secret Defenders, Strange Academy, Super Hero Squad, The Vi-Locks, Ultimates, Vizier's Guard, Witches