I hit Lux with my Charm as Ahri, but she just used her ultimate immediately like nothing happened. Is there something I'm missing about how charm works?
She probably started casting it right before you hit her, since CC doesn't interrupt it. The only way to stop Final Spark once the cast animation starts is to kill Lux.
Like Ezreal's ult, Lux's ult is not a channel or a cast, but merely an animation, so there's no way to stop her ult (with cc) once she starts casting it.
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