Did the opium trade have positive or negative impacts on the world?

The impact of the opium trade was wholly negative. Let's not forget that opium is a highly addictive substance, so the trade in opium brought the misery of drug addiction to millions of Chinese people who otherwise wouldn't have been affected.
One further negative consequence of the opium trade was that it reinforced Western imperialism, proving the imperialist powers with yet another instrument of domination and control. The opium trade was highly lucrative, so much so that the British Empire even went to war with the Chinese to protect it. The Chinese government wanted to put an end to this terrible trade that had caused so much misery to so many of its people, but the British weren't about to let go of a trade that raked in substantial profits. So they went to war, which they won easily due to their superior military technology.
In the aftermath of the Opium Wars, as they came to be known, China was crushed, humiliated, and impoverished. The British picked up where they left off, continuing to flood China with opium, which not only created more addicts but also strengthened imperial rule. Severely weakened as a consequence, China remained vulnerable to foreign exploitation.