The typical answers for who Nightwing’s nemesis is has a concusses of 2 possible characters: Blockbuster and Deathstroke. But why? Is it because Blockbuster has gotten the most time as a main villain for Nightwing while the rest were just his lackeys? Is it because Deathstroke not only has the Titans/Judas Contract connection where Dick became Nightwing and people just like to see the 2 highly skilled fighters go at it? But none of them SCREAM nemesis. Like where’s the chemistry? What will keep them coming at each other forever? I can’t find anything.
Looking at all the big nemesis’ in comics Batman/Joker, Superman/Lex Luthor, Professor X/Magneto, etc. They all have one thing in common: just like you can’t have light without dark, good without bad, a true nemesis is a character that represents the opposite of what the hero stands for - why they do what they do in the first place - they’re 2 sides of the same coin. Joker is the chaos to Batman’s order. Circe is the tyranny to Wonder Woman’s peace. Lex is the corruption to Superman’s ideal of justice. And I say Superman’s ideal of justice because justice is subjective. For Nightwing the easy way out is just to say he stands for justice but his view of justice isn’t the same as Superman’s or even Batman’s just like Batman and Superman have different ideals of what justice is.
Nightwing fights for the “little people” to take care of and protect those that are less fortunate or were done wrong by something bigger than themselves like the system itself. He’s trusting and see’s the best in people. To be a nemesis of Nightwing one has to see and bring out the absolute worst in people. And who could corrupt people in such a way? The Judge. To further make the case, it’s also important for Dick to protect good people from being murdered like his parents. The Judge not only corrupts people but he also kills them and we’re not just talking regular, old fashioned murder, we’re talking splatter movie killed (Similar to the recent Heartless but he doesn’t corrupt people so…)!
This also means he can see the worst in Nightwing and tempt him to unleash it because the thing about seeing the corruption in everything is that nothing’s perfect. People and everything we make or build have flaws. We all make mistakes or bad decisions. There is good and bad in everything and everyone. It is a constant challenge Dick has resisted his entire publication - becoming Batman and seeing the worst in the world and allowing it to take him over. And the more he resists the more Judge would want to corrupt him meaning he would follow Nightwing anywhere. It doesn’t matter where he goes or what city they’re in, they’re connected. To further make that case, with Judge being the one criminal Dick couldn’t catch and feeling like all the bodies he cumulates are on him, Dick would also follow him anywhere in order to get him.
The Judge is Nightwing’s true nemesis. If you wanna know more about the Judge read Sam Humphries and Brenard Chang’s Nightwing: The Untouchable.