Island whose eastern half is a sovereign state

New Guinea

Explanation:

The eastern half of the New Guinea island is a sovereign state. The name of the sovereign state is Papua New Guinea. Papua New Guinea is a country that falls in the category of the least developed countries in the world. It is also the country where there's one of the highest percentages of population that still lives like thousands of years ago in the dense tropical rainforests. It is a country that is rich in natural resources, but it is not the people from Papua New Guinea that see the benefit of them, but instead the international corporations. Initially, the whole island of New Guinea was supposed to be one country, the country of Papua New Guinea, but Indonesia had a military campaign and invaded the western half of the island and kept it, with the international community weirdly being totally silent about it. Also, the people that got under the rule of Indonesia were massacred, killed without any reason, tortured, lost most of their rights etc.