immitigable

adj

1. That cannot be mitigated

   “He was intent on an audacious, immitigable, and supernatural revenge.”

   “"Oh, my dear son, the plague in this town is raging with immitigable violence, and I am always fancying you will come home infected with it. […]"”

   “"[…] Matter is running down and the universe itself will one day become extinct. An everlasting and immitigable nothingness, in the void of black and absolute−"”