George Albert Smith, in the 1950 Conference Report, pg 169:

It will not be long until calamities will overtake the human family unless there is speedy repentance. It will not be long before those who are scattered over the face of the earth by millions will die like flies because of what will come.

Our Heavenly Father has told us how it can be avoided, and that is our mission, in part, to go into the world and explain to people how it may be avoided, and that people need not be unhappy as they are everywhere but that happiness may be in their lives—because when the Spirit of God burns in your soul, you cannot be otherwise than happy.

This was arguably fulfilled because millions did subsequently die like flies in events such as the Chinese famine of 1958-62. However, it is arguable that humanity has not yet been “overtaken” by calamities.

Still, it’s a rather curious prediction, generally, since deaths due to unnatural causes (i.e., things like famine and war) were about to decrease significantly over the next 70 years (compared with the past 50 years).

See this post for additional discussion.