IPA: /ɪˈmɪtɪɡəbli/
KK: /ɪˈmɪtɪɡəbli/
In a way that cannot be made less severe or serious.
The consequences of his actions were immitigably harsh, leaving no room for leniency.
Immitigably is formed from "in-" (meaning not) and "mitigare" (meaning to soften or alleviate) and the suffix "-ably" (meaning in a manner). The word describes a state that cannot be softened or alleviated, indicating something that is unyielding or relentless.
Think of 'not softening' ('in-' means not and 'mitigare' means to soften) to remember that 'immitigably' refers to something that cannot be made less severe.