Question

In Lancelot's efforts to rescue the queen in King Arthur's Knights, he creates great woe for Sir Gawaine. What does Lancelot do that causes Gawaine to become so upset?

Answer 1

a rift between two friends, Gawain and Lancelot, when the latter had inadvertently killed Gawain's two brothers, when Lancelot was rescuing Queen Guinevere from execution.

Answer 2

Answer: he killed Gawaine's brothers.

Queen Guinivere is sentences by King Arthur to burn to death due to her adultery.

When Lancelot finds out, he and his companions raid her execution, killing many knights including Gawain's brothers Gareth and Gaheris.

This created Lancelot and Sir Gawaine's feud.