All mega cities flattened. Hundreds of thousands of people next to nuke hits are blind and are fated to die as there is nobody to help them. Fires and destruction everywhere.

Toxic cloud rain the size of large city like New-York near insta-killing everything on its path as it moves with the wind. Hundreds if not thousands (one per each nuke) of toxic rain clouds at the same time and there is nowhere to hide from them. The only solution is to avoid them, but it is impossible due to destruction, debris, and loss of transportation due to EMP from nearby nuke. Mountains will not be safe largely due to toxic rains.

Loss of almost all food storage and drinking water to destruction and toxic contamination.

Even physically intact buildings and their contents may be unsafe after toxic cloud rains. People would not know of what is safe, since most don’t have means to measure radiation levels.

Inability to grow food for many years due to contamination.

Nuclear winter (there are some doubts on this topic as well as contamination).

Lack of food and drinking water. Deaths from starvation and dehydration. Deaths from taking contaminated water and food coming faster and more terrifying than from starvation.

Later on deaths from lower doses of contamination.

Survivors will envy the dead and follow the dead.

Only people in bunkers with years in supplies will have a chance.