There's still lots of Fog of War. If you're AP build Sweeper, if you're AD (especially ranged) build Lightbringer. Jump out of the Fog and hit him at least once. When he's back in the Brush he's still visible, start killing. Profit.
Or play a Kog, ult into the brush, and start killing.
Or Xerath's skillshot nukes.
If you know he's there, there's lots of characters who can hurt him without seeing him. Anyone with a skillshot, especially one that's long like Xerath or Ahri rather than small and round like Kog'Maw, can just start hitting the heck out of him.
Alternatively... just let him have it and take THEIR mid since they have fewer numbers. Ignore him and see how well he does. He gets gold, yes, but with almost no caps or kills he's a one-trick pony. He might as well wear a sign that says "I'M A DISTRACTION".