It was actually a super clean process on my end, couple of clicks on Amazon, they emailed me a QR code, I walked into the UPS store, flashed the QR code to them on my phone which they scanned, put the item on the desk and walked out.
Literally was in and out of the UPS store in less than a minute.
I have a lot of qualms about modern Amazon, mostly related to how value from Prime is continually diminishing in the form of things like ads in Prime Video, etc, but I have no convenience-related complaints about the return process I recently experienced.
Meanwhile returns through Whole Foods are a shit show. They can't give me a receipt for the return. "Just wait here and make sure you get an email confirming the return." Amazon claimed they never got one of my returns despite me having that email receipt. Had to fight it three damn times before they stopped pulling back my refund.
Unfortunately they force me to use Whole Foods (or maybe some other worse options) for any return with a lithium battery in it.
I found the return process to be wildly low friction. I didn't have to print or package anything. I initiated the return, and the next day an Amazon delivery driver came to my door and I handed them the unlabelled pack of batteries.