Depends on criteria, overall Saturn 5 but not because it WAS big, it was amazing on multiple levels. Next is Atlas, the only single stage to orbit LOx/Kerosene launch vehe. Yeah I can hear all you nah sayers w/o my computer but here's why.
Ground ignited engine plus ALL tankage goes into orbit. End of story Who cares if a few engines get dropped along the way, so does some propellant from those tanks which BTW were magnificent engineering marvels in themselves, cold worked 301 stainless steel 210 KSI tensile.
Thanks for your time,
KM
