What guarantee do you have that Amazon will delete it when you tell them to, though? It doesn't even necessarily come down to whether you trust Amazon ethically

What guarantee do you have that Amazon will delete it when you tell them to, though? It doesn't even necessarily come down to whether you trust Amazon ethically and legally, but also whether you trust their internal processes. Shredding the data on your own hard drive gives you a pretty good guarantee. Drilling a big gaping hole through it afterwards gives you an even better one.