Which barrier to intercultural communication competence is considered to be the most severe because it involves deep-seated feelings of unkindness and ill will toward particular groups?

Prejudice

Explanation:

Prejudice: In psychology, the term "prejudice" is described as an individual's incorrect, inappropriate, or unjustified attitude and is generally considered as negative towards the other person based entirely on his or her membership of a specific social group.

Example: An individual generally holds negative views about another person's gender or race and is referred to as a sexist.

In the question above, the given statement signifies "prejudice".