What is the oxidation state of an individual sulfur atom in so42-?

The oxidation state of single oxygen atom is - 2 since it is more electronegative and like to gain electrons.

The sum of the oxidation states of each atom = charge of compound

Let’s say the oxidation state of Sulfur is x.

Hence,

x + 4 * (-2) = - 2

x - 8 = - 2

x = + 6

The oxidation state of individual Sulfur atom is + 6