When you win so hard against someone they can't even bite the dust they would normally claw for: they were dusted.
Or first person: they can't even say they lost because of how badly they did so the individual couldn't even say they were dusted. So there's no really a first person.
I rose and transcended above some shit I already dusted so I wouldn't even count what I just did as dusting them until I had already dusted them in an afterlife sense, so they were dusted because I had done both; double dusted.