My "worst ever" road bike was also one of my "best ever", but for one flaw. It was a Litespeed-made Eddy Merckx Ti AX (EX?). The fit, steering geometry, ride quality and climbing performance were STELLAR.

The one thing that outweighed all of that was its high speed handling. The frame was so flexy that on high speed descents, any bump in the road was enough to send it off in some random direction.

I tried for a year to figure it out or get used to it, to no avail. To this day, it remains the only bike in 40 years of cycling that frightened me.