There exist certain categories of people who may never inherit from the estate of the mayyit under any conditions whatsoever. These are the true non-heirs. They may only receive a bequest of up to one-third of the mayyits estate if the mayyit left such a will behind. But beyond that, they have no right to the estate.
These people are different from the zaawil arhaam (who we refer to as “non-heirs” only for the sake of simplicity) and also different from those mentioned in the post Impediments to Inheritance.