You must mean a small tuna. A bluefin weighs up to 250kg / 550lb according to a quick search. Then again, if that hits you hard enough, it won’t hurt at all
Being hard and small, the tuna can can produce much more localised and sharp pain. If the whole tuna is dropped on your lower body from the third floor and turns it into mush it would also hurt though. But I still vote for tuna can.