He'd be about the right age, with a similar taciturn manner, and, of course, both characters are nameless. Both are active around the Mexican-American border, both work as bounty hunters, and both are fairly comfortable with death and violence while still having some moral compass. The kid is described as pale and thin, but with big hands and wrists, which isn't too far-fetched a description of the Man with No Name. The kid's eyes are described as oddly innocent; maybe that's why he squints all the time
If one is of the belief that the Judge is truly preternatural, then its not difficult to view him has being the dark enmity himself. In addition to his impossibly large knowledge of the world and his powers of teleportation and agelessness, the Judge encourages others to commit evil acts and act in heinous ways. His misanthropic views on humanity and war also support this. Finally, who's the one gang member besides the Kid that the Judge is most frequently at odds with? The priest, Tobin
He expounds on the power of science and reason and generally acts like the prophet of some twisted new faith. He is incredibly charismatic, and can bring people around to his way of thinking with his rhetorical skills. He regularly does the impossible, whether it be making gun powder from the resources he finds on a mountainside or feats of bi-location. His unusual appearance suggests something not entirely (or not even remotely) huaman
which fits with most of the Black Pharaoh's many forms. Additionally, his utter depravity and desire to corrupt, control, or destroy everyone around him fits with Nyarlathotep's views and general methodology. He doesn't age, he doesn't sleep, he says he will never die...