The South Face is the classic and most famous route on Lhotse, a very large and serious Himalayan face with sustained steep snow and ice climbing. It is objectively hazardous because of avalanche danger, serac exposure, altitude, and the need for multiple high camps.
Route Outline
Lukla/Khumbu approach -> Everest Base Camp area
Advance to the Lhotse South Face base and establish high camps
Climb the South Face through the central couloir system and steep snow/ice slopes
Gain the South Col area and continue on the standard upper mountain line to the summit
Descend by the same route