By the way, if SCF can converge in Gaussian, you can use Multiwfn to load .fch file, then use subfunction 2 of main function 100 to export GAMESS-US input file, the loaded wavefunction can be written as initial guess wavefunction in the file. In this case, if you use exactly identical calculation level in GAMESS-US as in Gaussian, the SCF convergence will be very easy to reach since the initial guess is perfect.

It is worth to note that if the basis set is large and especially when diffuse functions are heavily added, anion system is always somewhat difficult to converge. If there is no special reason, I suggest using other DFT functional instead of M06-2X, because it is well known that M06-2X is usually more difficult to make SCF converge. In addition, using "scf=conver=6", which has been mentioned in my blog article, is safe for present purpose, with this keyword the SCF convergence criterion is much easier to be reached.

No special actions if energy rises.
EnCoef did   100 forward-backward iterations
Restarting incremental Fock formation.
Restarting incremental Fock formation.
Restarting incremental Fock formation.
Restarting incremental Fock formation.
Restarting incremental Fock formation.
Restarting incremental Fock formation.
>>>>>>>>>> Convergence criterion not met.
SCF Done:  E(UM062X) =  -4021.89078842     A.U. after  129 cycles
             Convg  =    0.5974D-05             -V/T =  2.0070
<Sx>= 0.0000 <Sy>= 0.0000 <Sz>= 0.5000 <S**2>= 0.7948 S= 0.5222
<L.S>= 0.000000000000E+00
Annihilation of the first spin contaminant:
S**2 before annihilation     0.7948,   after     0.7518
DiagDN has N=  1317 LTot=  3985 but NE2=     3 cannot use DSYEVD.
Convergence failure -- run terminated.

The formulas for f+,f- which is many articles and multiwfn manual;

f+= q(N+1)− qN and f-= q(N)− q(N-1)   (page 387 in multiwfn manual) (1. Eq.) (N=charge 0, N+1=charge-1, N-1= charge+1)

Fuki calculation is given below in section ''Calculating global and atomic indices ''(page 679) in multiwfn manual

Units used below are "e" (elementary charge)
Atom q(N)        q(N+1) q(N-1)    f-         f+       f0       CDD
1(C ) -0.0587 -0.1185 0.0852 0.1439 0.0598 0.1018  -0.0841
2(C ) -0.0390 -0.1674 0.0268 0.0658 0.1284 0.0971   0.0626
3(C ) -0.0597 -0.1873 0.0319 0.0916 0.1276 0.1096   0.0360

If f+and f- are calculated for 1(C) according to equation 1;

f+= q(N+1)− qN=-0.1185-( -0.0587)=-0.0598
f-=q(N)− q(N-1)=-0.0587-0.0852=-0.1439

But obove the table are calculated as f+= 0.0598 and f-=0.1439  so  Do these formulas must arranged as follows?

f+= qN(r)-q(N+1)  (2. Eq.)
f- =q(N-1)-qN(r)

Which formula is correct for f+and f- (1. or 2. Eq.)?

Best regards