The single worst captcha I've ever had to this day was the « gift » of German hosting company 1&1, which managed to stonewall their customer support (I think) b

The single worst captcha I've ever had to this day was the « gift » of German hosting company 1&1, which managed to stonewall their customer support (I think) by putting it behind a captcha made exclusively of a string of the digit 1 and the lower case letter l in a font where they look nearly identical. I remember trying for an hour to get past it but never could. It left such a sour taste in my mouth that even 15 years later it's still engraved in my mind, and I refuse to ever do business with that company again.