Well, excluding wines that were flat-out undrinkable from bottle faults (like many Coturris) that might vary, or cork taint, here's a couple of the scariest commercial wines I can remember that I thought unfortunately were probably representative bottles:
NV Tombstone Red
From Arizona, this was just flat-out weird. A bit off-dry, with a strange
combination of flavors (salami, Concord grape jelly, and cherries. Is this made by the Tombstone pizza people? Not by winemakers, it seems. I thought we should put a warning tag on the bottle, so waitstaff wouldn't innocently try the leftovers.
Which started off with a Georgian red. Ah, Georgian wine. Yes, I know you've been all waiting for notes on the NV Tamada Khvanchkura, from the cradle of winemaking. My initial note says "semi-rancid grape juice", but I'm prejudiced in general against sweet reds.