How is electronegative used in determining the ionic or covalent character of the bonding between two elements

If difference of EN < 0.4, non polar covalent bond

If difference of EN is 0.41 - 1.69, polar covalent bond

If difference of EN > 1.7, ionic bond

Most are usually covalent (ideal type)

To get the difference of electronegativity, subtract the smaller atomic mass of the element from the bigger one.