In fact, Tiangong-1 isn't even the largest satellite to make an uncontrolled descent. Skylab, the US's first space station, crashed in Western Australia without injuring anyone in 1979. NASA’s 12-ton Upper Atmosphere Research Satellite had an uncontrolled descent in 2011 and landed safely in the Pacific Ocean.
Tiangong is an eight-ton craft, about ten times smaller than Skylab.
It's very unlikely you're going to be hit by a piece of the satellite. "The personal probability of being hit by a piece of debris from the Tiangong-1 is actually 10 million times smaller than the yearly chance of being hit by lightning," the ESA said in a statement. The odds of a piece hitting you are less than one in a trillion. You're far more likely to win the lottery.