I must admit that I don't consider any of my ereaders bad or 'the worst'.
I started off with the Bookeen Cybook Gen 3 back in the day, I believe their first eink reader and moved on via the basic kindle, Amazon Voyage right up to the lovely Kobo Libra 2 in white.
And each time I was grateful for what the device gave me over reading paper books.
OK, so the early ones were not so good as the later ones, may have needed a reading light, but they opened a whole new world to me