Electronegativity does not depend on the hybridized state.
Electronegativity increases as s-character increases. But why is that?
Hybridized state: The penetration of the s-electrons in the nuclues is higher than that of p-electrons. Therefore, if an atom has hybrid orbitals with greater s− character the electronic charge in such orbitals will remain closer to the nucleus of that atom. Thus, electonegativity of such an atom will be higher.
CH4 sp3 25% s - character
C2H4 sp2 33% s - character
C2H2 sp 50% s - character
Here, C2H2 will have the highest electronegativity.