If you are connecting on KA from CX, you should not need one.  If you are using any other airline, then you need a visa.  I think, if you are connecting on RA, you are exempt for a single transit even though you may have an RT ticket.  That means, if you are flying RA, you need  a visa for either the outbound or return trip.  You may, however, want to check with the airline to be sure.