im inclined to say the ewoks, only because they canonically defeated the technologically superior stormtroopers on endor. however, that also had in part to do with the fact that the ewoks were fighting in a familiar area, where they knew the landscape and had familiar resources and knew how to use them to their advantage. had the same battle been engaged on a planet familiar to the troopers and not the ewoks, the troopers would probably have easily flattened the ewoks and had time for tea. not to mention, it would be really difficult for a platoon of tanks to navigate endors landscape.