IPA: /ˈpɪtɪləsli/
KK: /ˈpɪtɪləsli/
In a way that shows no mercy or compassion; harshly or cruelly.
The storm raged pitilessly, leaving destruction in its wake.
Pitilessly → It is formed from "pity" (from Old French *pitié*, meaning compassion or sympathy) and the suffix "-less" (meaning without) combined with the adverbial suffix "-ly" (meaning in a manner). The word "pitilessly" means in a manner that is without pity or compassion.
Think of 'pity' as compassion and remember that 'pitilessly' means acting in a way that shows no compassion.