What does Lysander fear in "A Midsummer Night's Dream"?
In Shakespeare's "A Midsummer Night's Dream," Lysander's only apparent fear is losing his beloved, Hermia. Although she reciprocates his feelings and wants to be with him, their relationship is in grave danger. Legally, Hermia and Lysander cannot marry in their home city of Athens. Because Demetrius also wants to marry Hermia and Hermia's father Egeus prefers Demetrius as a suitor over Lysander, Egeus has promised Hermia in marriage to Demetrius.
The local law says that Hermia can't defy her father to marry Lysander. As Theseus explains in Act 1 Scene 1, she has two options under the laws of Athens to avoid being executed: to obey her father by marrying Demetrius, or, "To live a barren sister all your life" (line 74) as a nun in a temple of Diana. Facing these as the only legal options with Hermia must scare Lysander, because he shows no hesitation in eloping with her in defiance of her influential father and the law.
At the end of the scene, Lysander also indicates he is afraid he might lose Hermia by her choosing not to risk running off with him. He feels the need to implore her to not stand him up. He says, "Keep promise, love" (line 182).