Synonyms of the word

unpardonable

• adj. impossible to pardon; impossible to excuse or justify.

deadly

• adj. (obsolete) Subject to death; mortal.
• adj. Causing death; lethal.
• adj. Aiming or willing to destroy; implacable; desperately hostile.
• adj. (by extension) Very accurate (of aiming with a bow, firearm, etc.).
• adj. (informal) Very boring.
• adj. (informal) Excellent, awesome, cool.
• adv. (obsolete) Fatally, mortally.
• adv. In a way which suggests death.
• adv. Extremely.

inexcusable

• adj. not excusable.

inexpiable

• adj. that cannot be expiated or atoned for, unforgivable.

mortal

• adj. Susceptible to death by aging, sickness, injury, or wound; not immortal.
• adj. Causing death; deadly, fatal, killing, lethal (now only of wounds, injuries etc.).
• adj. Fatally vulnerable; vital.
• adj. Of or relating to the time of death.
• adj. Affecting as if with power to kill; deathly.
• adj. Human; belonging to man, who is mortal.
• adj. Very painful or tedious; wearisome.
• adj. (Britain, slang) Very drunk; wasted; smashed.
• n. A human; someone susceptible to death.

unforgivable

• adj. Not forgivable; inexcusable.