Debilitating is a formal word used to describe things that seriously impair strength or the ability to function.

// She suffers from debilitating migraines.

// The class helped him conquer his debilitating fear of public speaking.

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"Worry is such a debilitating thing that robs you of your energy ..." — Georgia Nicols, The Denver Post, 3 Apr. 2025

Debilitating describes things that cause serious impairment of strength or ability to function. The word appears in both medical and general contexts; someone can suffer from debilitating nausea or debilitating stage fright. An adjective that takes the form of a verb, debilitating dates to the mid-17th century, making it the youngest of a trio: its source, the verb debilitate ("to impair the strength of"), dates to the early 16th century, and the noun debility ("weakness, infirmity") has been in use since the 15th century. All come from the Latin word for "weak," debilis. Polyglots may recognize the influence of debilis in words from Spanish, Russian, Czech, Turkish, Danish, and many other languages as well.