According to Factvrse, the signs he carries mean “Never Retire” and “A kill a day”. Zeno is an interesting hunter because he follows a very strict code that some of his younger descendants disagree with: he doesn’t kill for pleasure, and he doesn’t kill the innocent. He only kills when he has a contract to do so. This makes him unique given his family’s notorious reputation and has also cemented him a place in the hearts of fans.
There’s no shortage of Reddit threads expressing their admiration for his character. In a Zeno character discussion thread full of admirers, Atzar87 explains why they love the character by saying, “He’s a badass old man and his appearances tend to be highlights of the arcs he appears in.” Other fans in this one Thread claim that their favorite moment with Zeno was his Dragon Dive attack on the palace, which unfortunately ended up hurting an innocent bystander and causing him to hesitate in the fight. But the hesitation makes sense. All of his confidence is fueled by his pride in his hunting skills, so much so that when he’s careless and hurts an innocent, he pauses to question his actions.
Eventually, he takes his job seriously enough to embroider those menacing words onto his clothes.