  Resistivity, Hall effect, magnetoresistance and DC magnetization were
measured in Mn and Zn doped Ba$_{0.5}$K$_{0.5}$Fe$_{2}$As$_{2}$ samples. It is
found that the Mn-doping can depress the superconducting transition temperature
drastically with a rate of $\Delta T_c$/Mn-1% = -4.2 K, while that by Zn-doping
is negligible. Detailed analysis reveals that the Mn-doping enhances the
residual resistivity ($\rho_0$) significantly, and induces strong local
magnetic moments ($\sim$ 2.58 $\mu_B$) which play as pair breakers. While the
impurity scattering measured by $\rho_0$ in the Zn-doped samples is much
weaker, accompanied by a negligible pair breaking effect. A possible
explanation is that the impurity scattering by the Zn impurities are mainly
small angle scattering (or small momentum transfer), therefore it cannot break
the pairing induced by the interpocket scattering and thus affect the
superconducting transition temperature weakly.
