I'd recommend: 1. Blocking all the IP addresses you've found. You can also block the entire Amazon IP range. No real users will be coming from there. 2. Con

I'd recommend: 1. Blocking all the IP addresses you've found. You can also block the entire Amazon IP range. No real users will be coming from there. 2. Contacting Amazon and sending them your logs and evidence. 3. Contact competitor and threaten legal action. Don't expect much from (2) and (3), but (1) should solve your problem quickly.