I've been using AdGuard for the past month or so, and while it does block all ads, I'm not sure how privacy friendly it is. When I created this thread, I should have specified that "best" doesn't equal "the one that blocks all ads" but especially also "the one that doesn't eat and process your data".
Now I kind of regret buying AdGuard a little bit, because it's Russian. Then again, since they moved it pretty soon to Cyprus, you may think it's the "good" Russians, who left Russia. But Cyprus is also associated with all kinds of shady stuff …
Also to those who joined the convo recently, you'll find some analysis of me on the previous pages of the Terms & Conditions of AdGuard, and basically it said it multiple places that it can share and sell all your data if you agree with it (and I suppose when you install it, and you click that "agree" button, you agree with it, by, well, who guess it, agreeing with it …).
In addition to that, Little Snitch (a software that tracks all your incoming and outgoing connections) shows me that with AdGuard, basically your ENTIRE traffic goes through AdGuard.
So maybe I should re-open a new topic and ask what's the best Ad blocker not just for blocking ads but for your entire privacy, because most of you guys in this thread are fixed on the ad-blocking part, but "best" for me doesn't include just that. Best means BEST, which means best in all categories, not just one chosen category. That's why I changed the topic title now to not attract people anymore who just want to discuss ad-blocking abilities and ignore the whole rest that I find very important.
And one more thing: All browser extensions fail this test imo, simply because browser extensions are a well-known security risk in browsers. So no browser extension can be a good answer here.