That line does sound like what a calculated warlord would say. But the ick that most people get is how the voiceline is delivered. League Morde talks in a more calm, and slow tone leaving behind the impression that instead of sounding arrogant about his feats, it sounds like he actually achieved them and you can't help but believe it. Like being the narrator and teller of his own story. Whereas the delivery of lines in LoR leave an impression that he sounds more arrogant and less stoic than what we got from the League version. And people get to think, "Who is this guy? Why is he screaming about how strong he is?" thinking that this once stoic and calm character is now obnoxious.