The key is 100% boycotting all services provided by a company. Wikipedia’s list of Amazon product/services as reference (https://en.wikipedia.org/wiki/List_of_Amazon_products_and_services).
Incidentally, I know entire neighborhoods that don’t have other grocery stores besides Target/Whole Foods, not to mention that AWS is the cloud computing industry standard… As a personal example, my vet-prescribed cat foods are manufactured by Purina, a subsidary of Nestlé (needless to say, a separate but also extremely evil large corporation)
Don’t aim for 100%. Just 90% would be good. Make it a point when buying something to look for someone else first. Often there is a widget.com company that sells the same thing for a similar price but they have experts to write up the description and so help you choose which of the 100 different manufactures is really best for you. Every brand says they have the best, but often there are differences an expert would know about that you will never figure out on amazon.
Amazon reviews are terrible - sure what you choose worked for your purposes, but almost nobody buys all 100 (or even 10 of them) and compares, and thus you don’t know if this works but should be a 3 star because of how much better something they didn’t buy is.