What word is the opposite of adornment?

There isn't one perfect opposite for "adornment." It depends on the context and what you're trying to express. Here are some possibilities:

If "adornment" means decoration:

* Plainness

* Simplicity

* Sparsity

* Austerity

* Nakedness

If "adornment" means embellishment:

* Stripping

* Deprivation

* Bareness

If "adornment" means enhancing beauty:

* Marring

* Disfigurement

* Ugliness

The best word depends on the specific situation.