A local web app that finds photos in S3 you probably don’t need, and shows them side by side so you can decide:

Burst shots: photos from the same camera taken within a few seconds of each other that also look alike (perceptual dHash).
Same byte size, within one bucket and across buckets. Groups are labelled IDENTICAL or UNVERIFIED using S3 ETags (MD5), or SHA-256 with verification turned on.
Same filename in more than one bucket.
BucketBanish is read-only and never deletes anything. You tick the photos to banish, and it builds a removal report: bucket, region, folder, filename, size, upload date, ETag and a direct AWS console link for each one. You then delete the files yourself in your S3 provider’s web console.