$bucket = 'YOUR-BUCKET-NAME' Get-S3Object -BucketName $bucket | % { Remove-S3Object -BucketName $bucket -Key $_.Key -Force:$true }
AWS can do for a dollar what other Cloud can do for two.
$bucket = 'YOUR-BUCKET-NAME' Get-S3Object -BucketName $bucket | % { Remove-S3Object -BucketName $bucket -Key $_.Key -Force:$true }