S3 with versioning enabled provides this. I'm not being naive when I say S3 really provides everything you might need. Its my observation over the last 13 years, dealing with tons of fires, that there has every been a situation where I couldn't retrieve something from S3.
Legally you might need an alternative. Going multi-cloud doesn't hurt - after all I do it. But practically? I don't think I would lose sleep if someone told me they only back up to S3.