I think I've gotten off light!
The worst t-shirt I ever had was the shirt that one of my sisters designed for us when we became a new colony of AEPhi. The front design was cute, a little spray of lily of the valley... but the back was an adaptation of the columns (our crest) with giraffes and such. It came out really badly. It was long sleeved, and we only had XL's made, so while the shirt itself was ok, the sleeves just bagged on my arms (I'm short). I wound up cutting off the front design and sewing it onto another shirt. (My sister was less than thrilled.)
The worst t-shirt my chapter ever produced was a bid day shirt. The front showed several of the Warner Bros. characters; the back had a picture of Porky Pig saying "Th-th-that's all folks!" (Our rush themes that year had absolutely nothing to do with Warner Bros. cartoons.) The screenprinters left out one of the colors and there was no time to reprint them, so we got them cheap, but they looked awful. Sisters had the option to buy a shirt for themselves. Um, no thanks.