How can you punish these people

So I ran into a player just running it down mid in my game and decided to look at their game history and its just months (yes months) of this person either inting or carrying, and i mean their kda was either 10+ or .26 with LITERALLY not figuratively no in between. So its obvious this person is a smurf and I would care less if they were doing it in just normal games(still a dick move) but this person is doing it in ranked as well. So how can you catch and punish these people? I mean its obvious the current system isn't catching this person or they wouldn't have gotten away with this for months. Anyone have any ideas?