• Dearth (noun)
English Meaning: A scarcity or lack of something.
Bangla Meaning: অভাব; অনটন; আকাল।
Example sentence: The region is suffering from a dearth of medical specialists.

• Abundance (adjective)
English Meaning: A very large quantity of something.
Bangla Meaning: অতিপ্রাচুর্য, প্রয়োজনাধিক পরিমাণ; প্রাচুর্য।
Example sentence: There was an abundance of food at the wedding.

So, Antonym of 'Dearth' - Abundance.

• Other options,
• Lack (verb transitive), (verb intransitive)
English Meaning: The fact that something is not available or that there is not enough of it
Bangla Meaning: অভাব ঘটা, ঊন ঘটা।
Example sentence: He lacks common sense.

• Poverty (noun) [Uncountable noun]
English Meaning: The condition of being extremely poor
Bangla Meaning: দারিদ্র্য; দরিদ্রতা; দীনতা; দৈন্য; দরিদ্রদশা।
Example sentence: Some 80% of Haitians live in poverty, and few have proper jobs.

• Shortage (noun) [countable noun, uncountable noun]
English Meaning: A situation in which there is not enough of something:
Bangla Meaning: কমতি; ঘাটতি; অনটন; অভাব।
Example sentence: There's a shortage of food and shelter in the refugee camps.

Source:
1. Accessible Dictionary by Bangla Academy.
2. Oxford Learner's Dictionary.
3. Merriam-Webster Dictionary.
4. Cambridge Dictionary.