What is the electron configuration for Og with a charge of 2-?
According to SCF Relativistic Hartree–Fock Calculations on the Superheavy Elements 118–131 J. Chem. Phys. 53, 2397 (1970), for neutral atoms:

119 $8s$

120 $8s^2$

121 $8p8s^2$

122 $7d8p8s^2$

123 $6f7d8p8s^2$

124 $6f^38p8s^2$

125 $5g6f^38p8s^2$

126 $5g^26f^28p^28s^2$

127 $5g^36f^28p^28s^2$

128 $5g^46f^28p^28s^2$

129 $5g^56f^28p^28s^2$

130 $5g^66f^28p^28s^2$

131 $5g^76f^28p^28s^2$

Later calculations reported in Electronic Configurations of Superheavy Elements J. Phys. Soc. Jpn. 65, pp. 3175-3179 (1996) are different starting with element 122:

122 $8p^28s^2$

123 $6f7d8p8s^2$

124 $6f^28p^28s^2$

125 $6f^48p8s^2$

126 $5g6f^48p8s^2$

127 $5g^26f^38p^28s^2$

128 $5g^36f^38p^28s^2$

129 $5g^46f^38p^28s^2$

130 $5g^56f^38p^28s^2$

131 $5g^66f^38p^28s^2$

However, Electronic structure of eka-thorium (element 122)
compared with thorium J. Phys. B: At. Mol. Opt. Phys. 35 (2002) 1693–1700 finds:  

122 $7d8p8s^2$

specifically agreeing with the 1970 paper and disagreeing with the 1996 paper. 

See A suggested periodic table up to Z[=]172, based on Dirac–Fock
calculations on atoms and ions Phys. Chem. Chem. Phys., 2011, 13, 161–168 for additional information.