SS: Broken by all standards, 0 counters.
S+: Should be banned or picked every match. Doesn't have to be first picked or banned but should be staple picks.
S: Less crucial to be in every game but are viable first bans and should be banned in second round. If unbanned, most likely should be picked. Every god S and should in every player's god pool of that role (IE every ADC should be comfortable with Freya, Ullr, and Hachiman)
S-: Too good to be any lower but barely short of S. Solid pick ups in nearly any if not all situations. Should only really be banned in second round, especially as target bans.
A+: Just above the focal point of balance. Shouldn't be banned too often if ever. Should usually be picked after the second banning phase. These gods are safe for comfort picks and counters. Picking these gods are far from a liability but require a bit more skill with the character to yield results. Strengths still outweigh weaknesses. Recommended to be able to play MOST gods in your role from here up.
A: Balanced. Strengths and equal weaknesses. Can be picked into most comps but would not suggest unless very comfortable with the god. Still good for counter picks.
A-: Not bad but would shy away from unless incredibly confident in your ability with the god or have a very strong counter pick. Requires a comp to be built around. If your god pool is getting drained to the point of having to search this far down, there's an issue. Either picks an bans got messed up big time, or you need to learn better gods.
B: Bad. Expect to lose. Only useful for really cheesy strats, you're actually a god with the character (like disgustingly good will 100% reliably do well. In which case, why not put that effort towards a better god?), or if you REALLY enjoy being bmed.
D: New. I still don't know where to put Cerberus. I don't play casuals so I don't know how he is. He seems pretty cool from what I saw in PTS but... that was PTS. I'd guess he's going to be between A and S.