IPA: /ˈmaɪtɪli/
KK: /ˈmaɪtɪli/
In a powerful or strong way; to a great extent.
She fought mightily against the challenges in her life.
Mightily → It is formed from "might" (from Old English "miht", meaning power or strength) and "-ily" (a suffix used to form adverbs meaning in a manner of). The word "mightily" means in a powerful or strong manner.
Think of the word 'might' which relates to power, and remember that 'mightily' describes doing something in a powerful way.