demoniac

Heartless is a related term of demoniac.

As adjectives the difference between heartless and demoniac

is that heartless is without a heart; specifically, without feeling, emotion, or concern for others; uncaring while demoniac is possessed or controlled by a demon.

As a noun demoniac is

someone who is possessed by a demon.

Ruthless is a related term of demoniac.

As adjectives the difference between ruthless and demoniac

is that ruthless is without pity or compassion; cruel, pitiless while demoniac is possessed or controlled by a demon.

As a noun demoniac is

someone who is possessed by a demon.

Demoniac is a related term of diabolical.

As adjectives the difference between demoniac and diabolical

is that demoniac is possessed or controlled by a demon while diabolical is extremely wicked or cruel.

As a noun demoniac

is someone who is possessed by a demon.

Diabolic is a synonym of demoniac.

As adjectives the difference between demoniac and diabolic

is that demoniac is possessed or controlled by a demon while diabolic is showing wickedness typical of a devil.

As a noun demoniac

is someone who is possessed by a demon.

As adjectives the difference between demonial and demoniac

is that demonial is (obsolete) of or pertaining to a demon while demoniac is possessed or controlled by a demon.

As a noun demoniac is

someone who is possessed by a demon.

As adjectives the difference between demoniac and demonian

is that demoniac is possessed or controlled by a demon while demonian is relating to, or having the nature of, a demon.

As a noun demoniac

is someone who is possessed by a demon.

As nouns the difference between taxonomy and demoniac

is that taxonomy is the science or the technique used to make a classification while demoniac is someone who is possessed by a demon.

As an adjective demoniac is

possessed or controlled by a demon.