Rizevim's thing is honestly more villain than antihero for me, but I see where the question comes from. He's not just rebelling against heaven for kicks; there's this weird, almost petulant drive that makes him compelling. Like, inheriting the Lucifer name but being stuck as 'the weakest Maou' because his power is conceptual—it breeds this unique resentment. His journey isn't about redemption or gaining strength, it's about proving a nihilistic point: that the world's foundations are rotten. The antihero element comes from how he targets systems, not just people. He wants to tear down Heaven, the Underworld, everything, not to rule but to see it all burn because he genuinely believes existence is flawed. That's different from a power-hungry villain.
What defines him most is the emotional disconnect. He doesn't revel in cruelty like some villains; he's almost bored, treating everything as an experiment. His 'evil' is cold, intellectual, and strangely passive-aggressive. The journey is watching someone with immense latent influence (being Sirzechs' son, having a Sacred Gear canceler) choose to be a catalyst for chaos rather than a leader. He's less an antihero on a personal arc and more a narrative device that forces everyone else to confront their own hypocrisies. His end is fitting—not a glorious defeat, but a dismissal that highlights how his grand nihilistic project was ultimately meaningless to everyone but him.