Unmitigable

a patient suffering from unmitigable pain

the unmitigable environmental impact of the proposed project

[T]hou [Ariel] vvaſt a Spirit too delicate / To act her [the witch Sycorax's] earthy, and abhord commands, / Refuſing her grand heſts, ſhe did confine thee / By helpe of her more potent Miniſters, / And in her moſt vnmittigable rage, / Into a cloven Pyne, […]

Oh for some few months of firmer health! This unmitigable disorder, which chains me to the chamber and the chair!

[…] Sleep, impiteous sleep, / Unmitigable, uncorruptible gaoler, / Come, cloak my senses with thy leaden robe,