Multireference methods are usually required for transition metal systems due to the partially filled d electrons. In this work, the single-reference equation-of-motion coupled-cluster method at the singles and doubles level for double ionization potentials (EOM-DIP-CCSD) is employed to calculate energies of states from the d8 configuration of late-transition metal atoms starting from a closed-shell reference. Its results are compared with those from the multireference Fock-space coupled-cluster method at the CCSD level (FSCCSD) for DIP from the same closed-shell reference. Both scalar-relativistic effects and spin-orbit coupling are considered in these calculations. Compared with all-electron FSCCSD results with four-component Dirac-Coulomb Hamiltonian, FSCCSD with relativistic effective core potentials can provide reasonable results, except for atoms with unstable reference. Excitation energies for states in the (n - 1)d8ns2 configuration are overestimated pronouncedly with these two methods, and this overestimation is more severe than those in the (n - 1)d9ns1 configuration. Error of EOM-CCSD on these excitation energies is generally larger than that of FSCCSD. On the other hand, relative energies of most of the states in the d8 configuration with respect to the lowest state in the same configuration are predicted reliably with EOM-DIP-CCSD, except for the 3P0 state of Hg2+ and states in Ir+. FSCCSD can provide reasonable relative energies for the several lowest states, while its error tends to be larger for higher states.