The #1 worst thing isn't a topic for this forum, so here's my #2 worst thing about my current country and more specifically the region where I live:
Grass pollen. From May till around mid-July (just in time for my birthday) it is SO BAD. I didn't use to be allergic to pollen, but something about either the different species of grass in this country or the sheer amount of pollen has changed that. It is utter agony and suffering, with a nose that will. not. stop. running for months. Antihistamine pills help, but don't eliminate the symptoms completely.