Answer:
A one world-government could be a positive outcome for manking, but also a negative one.
It could be positive in the sense that it would allow a better coordination to solve global problems like climate change or world poverty. In fact, one of the problems of climate change is that the solutions need to be on a global scale, and countries do not agree on them.
It could be negative if only a few nations take control of the world government, and use it for their benefit, instead of the global benefit.