One is disenchantment, which, I conclude, will have to be just nullifying magic. Perhaps indiscriminately?
The other is, of course, spell-specific. But I'm really going to have to work out some ways that someone might resort to it instead of to disenchantment on top of the possibility that disenchantment is an area effect without discrimination. After all, the situations where I am thinking of using it, they've already had to assume they have to be able to do everything necessary mundanely because of other people's disenchantments; their own, they would be ready for.
I suspect there's going to have to be a counter for disenchantment. Or at least a way to deflect it from vital enchantments.
At any rate, a reason why you might need someone good with magic even if not very useful with the mundane substitutes.