Worst Episode?
I think the most laughably bad episode was the one Chad Michael Murray wrote.
It was so community theater, set, for no apparent reason, in the 1930s. It had every cliche about the 1930s that someone who knew nothing about the 1930s would put in. Why was this vanity allowed to happen. It had nothing to do with One Tree Hill and everything to do with CMM's enormous ego -- and lack of writing talent.
That episode also had the worst moment of acting in the whole series. I forget the line, but Peyton was with Lucas on a bridge and Peyton twirls around and says something with the most amateurish line reading ever. It's begging for an animated GIF.