Odo. He has the ability to morph into anything, and provided he is witty, would find a way to shut Data down. Data has superhuman strength but not the ability to morph, so he would have to get a hold of Odo before Odo manages to slip into and disrupt Data's processes.
Well Odo can't actually morph into anything, his species can but Odo is hardly a master shapeshifter. I think it also worth factoring in the fact that in addition to superhuman strength Data hasa a superhuman intellectual capacity.
Data would just figure out how to expose him to plasma coolant