Miagani Island: Riddler Victims
This plaza is located in West Kingston, and the switch to trigger the Riddler message is on a rooftop overlooking the area. Use the Remote Controlled Batarang to find the victim, then send another one through the electricity on the Ferris Mall sign to knock him out.
This victim is found immediately west of Wayne Tower; the Riddler pad is on a rooftop overlooking the nearby plaza. Find the victim with the Remote Controlled Batarang, then send it through the current at the far end of the plaza (above the K.G. Bagels sign) to stun him.
The Riddler pad is on an overpass near Miagani side of the bridge. Do the usual, but this time you'll actually have to shoot the victim with the Remote Electrical Charge.