Nelson is the easiest bot and this is how to beat him
Yah, Nelson is awful with the Black pieces. I think Nelson's "purpose" is to help people learn how to defend as Black against early Queen attacks by White though, where Nelson goes for Scholar's Mate. For those just starting out with chess, Nelson can be a real pain, but once you sort out how to get beyond his initial nonsense he tends to fall over.
I just got my highest every score (98.2) in a game against Nelson. I think he had an off day, because he was very sloppy. But either way, you win by pushing his queen around: