2 cases arises:
First, The earth suddenly stoped rotating. It would be painfull for everyone as earth’s velocity at its surface is about 1600 km/h. That means the land will suddenly move at 1600km/h.
Imagine you are sitting in your room and the wall suddenly came to u at such a high speed.
Those people who are outside their homes are not safe too, 1600km/h speeding wind will blow everything apart but not before the demolition of skyscrapers by their own inertia.
Everyone who is in contact with land will die. But I believe that only about 70,000 people will be alive to see this misery on our planet but they will also die when their plane will land on 700km/h(relative) moving runway.
The costal areas whould be quiet dramatic as on western side of India there would be huge tsunami kilometres high whereas on eastern side the scenario would be opposite where the ocean bed will be visible.
It is also possible that because of such big force the earth gets torn apart.
Second, The earth slowly decreased its rotation in few years or so.