Natalie Portman delivers an utterly fearless performance in “Love and Other Impossible Pursuits,” playing a bitter, borderline unlikable Manhattan home-wrecker subsumed by grief over the death of her infant daughter. As in his three earlier features, writer-director Don Roos (“Happy Endings”) relishes true-to-life emotional complications, to the point of sacrificing both narrative cleanliness and universal appeal. Unsparing in its microscopic inspection of damaged characters, including Lisa Kudrow’s comically angry wronged wife, “Love” tests the limits of a viewer’s tolerance for pain and should garner significant respect from those who like their upscale melodrama on the lacerating side.

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In her strongest screen work since “Closer,” Portman, appearing in every scene, often a touch disheveled, dares to inhabit a character who’s more comfortable expressing resentment than love, and who seems temperamentally incapable of achieving grace even or especially when she tries for it. Portman’s decision to show us tiny glimpses of Emilia’s yearning for acceptance by those around her, harmful though it may be, is what tips the scale on the character, making her ever so slightly redeemable to both Roos and the viewer.