For any or all of them to be within the realm of feasibility there is only one word that would make such happen and that is COOPERATION.

I would go for ending hunger. That would decrease wars and eliminate some medical conditions (while increasing other medical conditions.

End wars. The other two are often the creation of war anyway, and are more easily solved in a world at peace.

Curing/eliminating all disease/illness would probably have the greatest long-term impact on the world. War will eventually happen at some point in the future and there are numerous causes of hunger that could cause it to happen again at some point. But if disease and illness are eliminated, they wouldn't return. New diseases might arise at some point but that would happen anyway.

Of course.

To end world hunger would require also ending wars/physical confrontations. Eliminating disease/illness would also end they cycle of replenishment/new growth/change so be an insult to evolution. That seems unwise.

Only the first option is feasible.