My 2 problem lines are Williams' - both going back only to the late 1800s, otherwise I've got 12 lines going back in to the 1700s, and 2 others going into the 1650s, the best one though is a registered death in 1451. Working back from my daughter, thats 20 generations.
With that one though I must admit it wasn't my work, but notes that a great aunty of a newly found cousin had put together (they were gentry, and had everything written down in a family bible, which has since been confirmed with parish records etc.) - so we swapped. What he had in depth, going back, I had in width coming up to the present day. We met about 1820 ish.