Clindamycin
"I had a bad skin infection that turned into a blood infection rather quickly- while this antibiotic kicked its ass it also kicked mine. I was on 500 mg 3 times a day for about 2 weeks (starting off with IV and then when I was discharged pills) 

The side effects I experienced was like a living hell. I'd rather cut off my leg than take them again. 
Heart burn, metallic taste, my skin started peeling off on my hands, face, and legs. My eczema broke out terribly, but my acne cleared up so there's that. 
But the worst part was the diarrhea and nausea. I feel so faint and tired, 24/7, no appetite and my stomach feels like I have bowling balls in it. I've been vomiting almost every day along with non stop diarrhea. It works. But its HELL. even after you stop"