In Kate Chopin's novel The Awakening, what characters could be considered antagonists, and why?

In Kate Chopin’s novel The Awakening,
various characters might be considered antagonists, including the
following:

• Edna Pontellier becomes increasingly
  antagonistic toward her husband, Léonce. Léonce, it is true, antagonizes Edna in one of
  the early chapters of the book, when he returns home from a night of drinking and
  gambling and accuses her of paying insufficient attention to the children. He also
  antagonizes her later when, back in New Orleans, he accuses her of paying insufficient
  attention to her social responsibilities.  As the book develops, however, Edna becomes
  increasingly distant from, and antagonistic toward, her husband, as when she moves out
  of their home and also when she engages in romantic affairs with two other
  men.


• Those two other men – Robert Lebrun and Alcée
  Arobin, also have antagonistic feelings toward one another.  Robert, in particular,
  dislikes the free-wheeling, amoral, indeed even immoral Alcée. Robert distrusts Alcée’s
  interest in Edna


• Ironically, for part of the novel, Edna
  is in a somewhat antagonistic relationship with Robert, the man she thinks she truly
  loves. When Robert realizes that his relationship with Edna is becoming too serious, he
  leaves the immediate vicinity and goes to Mexico. This sudden decision on his part
  annoys and vexes Edna.


• As Edna’s friend, Adèle
  Ratignolle, begins to realize that Edna is growing too fond of Robert and that Edna
  later has begun an affair with Arobin, Adèle becomes a kind of friendly antagonist
  toward Edna.  It is largely because of warnings from Adèle that Robert decides to leave
  Edna, and it is Adèle who later warns Edna that she risks both her reputation and her
  relationship with her husband and children (especially the latter) if Edna continues her
  relationship with Arobin.


• Edna’s relationship with her
  visiting father, the Colonel, is not especially close, and although she gets along with
  him better than she had expected, he is an antagonist in the sense that he advises
  Léonce on her to handle women with proper masculine
  control.


• Ultimately, Edna comes to regard even her
  children as antagonists who may enslave
  her:

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The children appeared before her like antagonists
who had overcome her; who had overpowered and sought to drag her into the soul's slavery
for the rest of her days. But she knew a way to elude
them.

• However, her
  larger antagonist (it might be said) is the social system of her period, which has
  helped dictate her marriage and the nature of her marriage and which is at the root of
  much of her sense of being constrained and
  unfree.