Okay let’s break this down into the three unrelated parts:
Which genocides? Sounds to me like you know that the genocides you’re referring to actually have huge amounts of evidence, so you’re intentionally avoiding saying which specifically to avoid scrutiny.
Most genocides ever committed? The country has only existed since 1776, and humans have been committing genocide for a hell of a lot longer than that.
none that they actually discovered via authentic journalistic investigations
What the hell is that meant to mean? Who is “they”? None of what? What makes a journalist’s investigation “authentic”?