Is there anyone in your story who has the following attributes most of the time?
• The person portrays himself or herself as self-sufficient, needing nothing, vacuum-free.
• The person pretends to have no requirements and doesn’t recognise real needs in others.
• The person tries to fill the needs of others without consultation, based on his or her own opinions or judgements.
• The person has a thick shell, resistive to anyone’s needs, including their own.
• The person is a ‘world-builder’, extending his or her own perception of reality, trying to fill any vacuum around him or her with this or her own ideas of what is needed or wanted.
• The person stamps or tries to stamp his other own image on everything in the environment.
• The person puts power ahead of everything, not particularly because he or she is 'power-mad' but simply as an extension of what he or she is.
That’s your antagonist.
The antagonist is simply the personality which results when needs become invisible.
How does the protagonist tackle this?
By making vacuums visible.
In other words, by finding the hidden need, gap, hole, weakness, flaw, craving, emptiness, desire.
Vacuums - needs, gaps, holes, weaknesses, flaws, cravings, emptinesses, desires - create motion. Take them away and things grind to a halt. The antagonist is the stuck character, unmoving, undeveloping, unseeing. The antagonist is the anti-need, the self-satisfied self, the vacuum-defier, unable to appreciate or denying that he or she has needs that can be met.
You’ve probably already spotted that this is exactly what protagonists in stories do to their adversaries: find the gaps, holes, flaws, and exploit them.