Synonyms of the word

unrelenting

• adj. Not relenting; having no pity; not being or becoming lenient, mild, gentle, or merciful; unyielding; inflexibly…

continual

• adj. Recurring in steady, rapid succession.
• adj. (proscribed) Seemingly continuous; appearing to have no end or interruption.
• adj. (proscribed) Forming a continuous series.

grim

• adj. dismal and gloomy, cold and forbidding.
• adj. rigid and unrelenting.
• adj. ghastly or sinister.
• adj. (Britain, slang) disgusting; gross.

implacable

• adj. Not able to be placated or appeased.
• adj. Adamant; immovable.

inexorable

• adj. Unable to be persuaded; relentless; unrelenting.
• adj. Impossible to stop or prevent; inevitable.
• adj. Adamant; severe.

persistent

• adj. Obstinately refusing to give up or let go.
• adj. Insistently repetitive.
• adj. Indefinitely continuous.
• adj. (botany) Lasting past maturity without falling off.
• adj. (computing) Of data or data structures: existing after the execution of the program. Remaining in existence…
• adj. (mathematics) Describing a fractal process that has a positive Brown function.
• adj. (mathematics, stochastic processes, of a state) non-transient.

relentless

• adj. Unrelenting or unyielding in severity.
• adj. Unremitting, steady and persistent.

stern

• adj. Having a hardness and severity of nature or manner.
• adj. Grim and forbidding in appearance.
• n. (nautical) The rear part or after end of a ship or vessel.
• n. (figuratively) The post of management or direction.
• n. The hinder part of anything.
• n. The tail of an animal; now used only of the tail of a dog.
• n. A bird, the black tern.

unappeasable

• adj. not able to be appeased or satisfied.

unforgiving

• adj. Unwilling or unable to forgive or show mercy.
• adj. Having no allowance for weakness.