Hardest approach?
Hmmm... Circling a 737 or a 757 to runway 28 at La Paz/Bolivia, at 14,500ft, with gust wind and downdrafts over the city, located no more than 2 miles from runway threshold.... or circling an A320 or a 737 to runway 02 at Santos Dumont airport, Rio de Janeiro/Brazil, at night... truly exciting!
By the way... La Paz airport is 13,300ft above sea level and Santos Dumont airport main runway lenght is no more than 1,300m and west sector (where the circling area is) has high mountains and airplanes must be fully configured prior to turn base.
Bkmk