i'm very busy rn, so i don't have time to give a proper reply and it would probably be draining for both me and you. i'll just give a brief one to start you off with, and i'm hoping you'll engage it in good faith. however, there's lots of information on amnesty being a western political tool to encourage regime change. i will link a few sources for you to get started.
first of all, i will point out that amnesty international is an NGO. they have a long history of being tied with the UK government, and get regular grants from the United States State Department and other pro-western governments (obviously including the UK). not even getting into their history against the global south, that alone makes them incredibly unbiased and obviously a tool for western propaganda. imperial core governments are not regularly funding NGOs who are critcising them in a way that has any material effect.
i'm not sure if you know how terrible NGOs are/their history in regime change, but if you don't know - this video will get you started: https://www.youtube.com/watch?v=NzIJ25ob1aA&t=1s
i will just link to a few articles about amnesty international, they are not at all a good source. i would like to also point out, that you want a good source that "isn't affiliated with any countries amnesty has investigated" which:
1. rules out any country being able to defend themselves with primary sources, very much the opposite of what most professionals researchers do. this would leave you to only believe only outside sources - further away from what is happening and thus leaving much more chance for inaccuracies. there should be a healthy balance of both, with primary research and countries being allowed to defend themselves (if the evidence cannot be disputed).