Stalin was certainly a lunatic, but not sure he was a fascist.
It's an interesting one though, because this is where the labels of left and right (far left/far right, fascism/socialism, communism) have blurred lines.
Stalin was certainly a believer in totalitarianism and he was quite an extreme nationalist, so there are certainly parallels with the other European fascist regimes of the 1930s. However, his economic policy was founded on collectivisation and state control, whilst fascism is founded on corporatism, so Stalin is more communist in this sense.