Wonder woman is the only one that I think is 3-7 or possibly even 2-8.
But other characters I think Grodd struggles with:
Robin - Better neutral, punishes stampede free for big dammy, interrupting mb sword flip is big risk small reward for Grodd.
Joker - Teeth make it incredibly hard to approach him and his setplay is absurd. Saving grace was he had no good wake-up but lol patch. Not awful but bad.
Batman - I just fucking hate this potato ass character, j2 nerf made no difference cause grodds hitbox is huge and he still pretty much always has a bat. Our projectile immunity is great in the MU but its far too hard to get out and doesn't last long enough to be massively effective and can easily be stalled out.
Cheetah - Grodd struggles to deal with her leap and constantly has to play at her pace, this one is potentially not bad but I can't say I look forward to fighting her.
Supergirl - yeah
Catwoman - yeah
Black Adam - Very good at taking advantage of how unsafe Grodd is, I don't hate this matchup because it's kinda fun even though it's difficult.
The Flash - He is basically just a much better version of Grodd, j1 is very difficult to deal with and Grodd can't nj out b22 pressure.
MUs that I'm too stubborn to admit are bad but probably are (especially post patch): Atro, Blue Beetle, Dr Fate, Firestorm, Green Lantern, Harley, Scarecrow
MUs I think we win: Darkseid, Deadshot, Black Canary
The rest of the cast are matchups that are even or I don't play enough.
I go through phases of up playing and down playing Grodd so maybe I'm just in a downplaying phase cause I'm tired of all the dumb shit in this game
Also latest patch was pretty bad for us since a lot of our even or winning MUs got buffed. Batman nerf wasn't significant in the Grodd MU apart from the meter build change, Deadshot nerf was welcome but Grodd handled him well anyway, and I have no idea about the Red Hood matchup outside of ranked.