You could try this sample line to delete all at once. Remember that this is highly destructive, so I hope you know what you are doing:

for bucket in $(aws s3 ls | awk '{print $3}' | grep my-bucket-pattern); do  aws s3 rb "s3://${bucket}" --force ; done

You are done with that. May take a while depending on the amount of buckets and their content.

I did this

aws s3api list-buckets \
   --query 'Buckets[?starts_with(Name, `bucket-pattern `) == `true`].[Name]' \
   --output text | xargs -I {} aws s3 rb s3://{} --force

Then update the bucket pattern as needed.

Be careful though, this is a pretty dangerous operation.

The absolute easiest way to bulk delete S3 buckets is to not write any code at all. I use Cyberduck to browse my S3 account and delete buckets and their contents quite easily.