Hello, y'all.
I'm new to this board, having only recently figured out it was here, and I'd really appreciate your help with a problem. I need a word!
I have a definition, and I know there must be a word out there that suits the meaning, but I can't find it.

The word I'm seeking will be one that can be used to label (we all know at least one person to whom this word will apply) someone whose ass cannot be kicked hard enough for edification or satisfaction. I don't know if this word already exists, or if someone will be able to coin one.

Thanks for you input,
Frank