IPA: /ˈdɛvəsteɪtɪŋli/
KK: /dɛvəˈsteɪtɪŋli/
In a way that causes great damage or destruction.
The storm devastated the town, and the aftermath was devastatingly clear.
Devastatingly → It is formed from "devastate" (from Latin "devastare", meaning to lay waste or destroy) and the suffix "-ingly" (meaning in a manner of). The word "devastatingly" means in a manner that causes great destruction or distress.
Think of the word 'devastate' which means to destroy, and remember that 'devastatingly' describes doing something in a way that causes great destruction or distress.