Well they introduced him with a backstory of killing a infamous Elite black-ops leader, then had him officially show up in Halo Wars 2 beating the shit out of three Spartan II's from Red Team (Alice, Jerome, and Douglas), and now he manhandled John like its nothing. He's not an evil character technically like Truth, Regret, or Mercy but he's a Chaotic Neutral, someone who just wants freedom so how their gonna justify John fighting him or him going down is tough. Especially since all the hype for Atriox outside of Halo Wars 2 comes from comics and novels and none of that was done by 343 Studios.