What was the most dreaded thing for immigrants on Ellis Island?

The disease most feared was trachoma, a highly contagious eye infection that could lead to blindness and death.

Explanation:

At one time, the average passenger mortality rate was 10 percent per voyage. The conditions were so crowded, so drearily dark, so unsanitary and so foul-smelling, that they were the single most important cause of America's early immigration laws.

Explanation:

i got this from https://hilo.hawaii.edu/news/kekalahea/journey-through-ellis-island-2017#:~:text=At%20one%20time%2C%20the%20average,of%20America's%20early%20immigration%20laws.