The antonym of 'Effrontery' is -

- উল্লেখিত প্রশ্নে Effrontery এর antonym হচ্ছে Kindness.
Effrontery(noun)
English Meaning: Insolent or impertinent behavior.
Bangla Meaning: ঔদ্ধত্য; নির্লজ্জ সাহস।
Synonyms: Shamelessness (লজ্জাহীনতা), Impoliteness (অশিষ্টতা), Disrespect (অসম্মান; অশ্রদ্ধা), Arrogance (অহমিকা)।
Antonyms: Timidity (ভীরুতা), Fear (ভয়), Cowardice (কাপুরুষতা), Shame (লজ্জা), Kindness (দয়ালু)।

Example Sentence: 
1. He then committed several acts of brazen effrontery.
2. The little squirt had the effrontery to deny eating any cookies, even with the crumbs still on his lips.

Source: Lecture.