Orochimaru, though at the moment its a bit unclear but if u look at their past actions it should be Oro.
Granted Madara did kill more people most likely, but that was in a time of war, it was either kill or be killed.
On the other hand orochimaru kidnapped people (baby's) experemented on them, like in yamato's case, where he used 60 baby's as guinea pigs and only 1 survived :|, Madara never did such things , he fought because it was war and he had to defend his clan's honour and his clanmembembers.