Gary Ridgway is the worst if you define worst by sheer verified number of victims.
Albert Fish possibly killed more, and perhaps Bundy did also, but those murders have not all been verified.
Henry Lee Lucas self reported hundreds of murders, but his claims have been discounted.
There was some loony tune who was convicted of a handful of killings who called himself "Coast to Coast".
Harrier will have to look him up - he is somewhat obscure - but his first name was Tommy and he was arrested in Texas.
Here he is - Tommy Lynn Sells.
http://www.youtube.com/watch?v=VZPCJ5_nT00