I guess depending on your deck wouldn't Scarlet Witch (avenger) negate his effect as well?

She wouldn't, she can be responded to because both work during the combat phase. We're talking about JLA limited though.

BWA HA HA HA would also work, right?

Lets Not OFrget Funeral For a Friend also will get you out of it.

There is also Sinister Citidel. There are many ways to force them to use it Early so you can try and play around it. Hal Jordan (6) and the Mist are some of my favorite movers. The General also Makes him use it at the begining or not at all.

My Favorite option is the Citidel, but thats because its reuseable and non Unique. Not to mention if you have one From draft thats one more the guy playing Grodd doesnt have.