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Energy differences between frozen core and all electrons correlated.
MP2, MP3, MP4, B2PLYP, CCSD, and CCSD(T)

For Cl2- (chlorine diatomic anion)

Energies in Hartree
Methods with standard basis sets
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z aug-cc-pV(T+d)Z
Moller Plesset perturbation MP2=FULL 0.000000 -0.008720 -0.023495 -0.005346 -0.019696 -0.019696 -0.020895 -0.097447 -0.097447 -0.038777 -0.053715 -0.011779 -0.065487 -0.124423 -0.013714 -0.068385 -0.125732 -0.207340 -0.210051
MP3=FULL         -0.018020   -0.033757       -0.051610 -0.010228 -0.061839         -0.201170 -0.203834
MP4=FULL   -0.007995     -0.018262       -0.097158     -0.010474 -0.063284   -0.012431 -0.066239   -0.203769 -0.206535
B2PLYP=FULL 0.000000 -0.002653 -0.007067 -0.001623 -0.005915 -0.005915 -0.006273 -0.028096 -0.028096 -0.011579 -0.015769 -0.003574 -0.019490   -0.004150 -0.020312   -0.060441 -0.061205
Coupled Cluster CCSD=FULL         -0.017832           -0.051494 -0.010125 -0.061692 -0.119877 -0.011915 -0.064496 -0.121112 -0.200929 -0.203537
CCSD(T)=FULL         -0.018241           -0.052350 -0.010470 -0.063096 -0.122156 -0.012351 -0.065984 -0.123436 -0.203300 -0.206039
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z aug-cc-pV(T+d)Z