Tsunade's, by a decent margin.
Anybody can get SM as long as they train and have the chakra reserves to master it. His other jutsus don't seem to require that much skill (Jiraiya was never about that anyway).
Part of Orochimaru's arsenal comes from his experiments, its not about about mastery really. The other part is about multiple versions of the summoning jutsu, not a very complicated jutsu to master.
Tsunade's jutsus require the utmost chakra control and skill, no other character but Sakura is able to replicate her feats.