A single crystal of isovalently substituted Ba(Fe$_{1-x}$Ru$_{x}$)$_2$As$_2$ ($x=0.24$) was sequentially irradiated with 2.5 MeV electrons up to a maximum dose of $2.1 times 10^{19}$ electrons/cm^2. The electrical resistivity was measured textit{in - situ} at $T=$22 K during the irradiation and textit{ex - situ} as a function of temperature between subsequent irradiation runs. Upon irradiation, the superconducting transition temperature, $T_c$, decreases and the residual resistivity, $rho_0$, increases. We find that electron irradiation leads to the fastest suppression of $T_c$ compared to other types of artificially introduced disorder, probably due to the strong short-range potential of the point-like irradiation defects. A more detailed analysis within a multiband scenario with variable scattering potential strength shows that the observed $T_c$ vs. $rho_0$ is fully compatible with $s_pm$ pairing, in contrast to earlier claims that this model leads to a too rapid a suppression of $T_c$ with scattering.
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