The US has been the de facto leader of the imperial core since WW2, and its government is thus directly or indirectly responsible for a large part of the suffering in the world right now — be it directly through wars, genocides/massacres, sanctions, embargoes, or indirectly through economic imperialism or neocolonialism — so yes, that should be the first country anyone comes up with. Probably also because I happen to be from one of its victim countries.

China has an active genocide

All claims of this come from imperial core countries or "independent" orgs funded by its corporations.

The Organization of Islamic Cooperation and delegates from dozens of Global South countries approve of China's handling of the ETIM (a problem deliberately created by the US through Afganistan by the way) and deny western claims. This lines up with what the hundreds of millions of annual tourists to the region say.

Between the western govs responsible for killing, and continuing to kill, millions of muslims in the past few decades alone throughout Africa, Middle-East, Asia, and global south countries without a recent history of doing so (they are the victims rather), I for one know which not to trust.

Russia

The US colony has killed three times more civilians in its genocide in the past few months than the Russian military has in 2 years in its proxy war with the US. This isn't remotely comparable.