Helaman 4:20

And it came to pass because of the greatness of the number of the Lamanites, the Nephites were in great fear, lest they should be overpowered, and trodden down, and slain, and destroyed;

Because the Lamanites had so many people, the Nephites were very afraid. They were afraid they would be beaten, stepped on, killed, and destroyed.

Because the Lamanites were so many, the Nephites lived in constant fear of being overwhelmed, trampled, and destroyed.