The noble gas with  highest positive electron gain enthalpy is

Due to stable configuration noble gases have positive electron gain enthalpy

Correct order of positive electron gain enthalpy is  $\mathrm{Ne}\left(116\right)>\mathrm{Ar}\left(96\right) =\mathrm{Kr}\left(96\right) >\mathrm{Xe}\left(77\right) >\mathrm{He}\left(48\right)$

This may be because the valence shell of helium is 1s, having the lowest energy thus easier to put another electron in the next subshell that is, 2s.

If we talk about Ne ,we have to first overcome the 2p energy and should have enough energy to loose when Ne accepts another electron in much higher energy level that is,3s(to be least stable)