Destroying the Dawnguard is a quest available in The Elder Scrolls V: Dawnguard.
The quest can only be accepted once "Kindred Judgment" has been completed.
"The Dawnguard will, no doubt, soon become even more of a nuisance now that Auriel's Bow has been recovered. We need to strike a crippling blow against them before they muster more men against us.
They've holed up in an abandoned fort in the Rift. Killing their leaders should discourage an all out war with us."
In order to complete the quest, the Dragonborn must travel to Fort Dawnguard and simply kill the leaders who are indicated by objective markers. The leaders are:
| <questgiver> has sent me to destroy the Dawnguard leaders at Dayspring Canyon.
|<questgiver> sent me to Dayspring Canyon where I destroyed the Dawnguard leaders.