Star Trek: 10 Best Klingon Episodes
6. The Next Generation - Redemption I & II
A two part episode, "Redemption" was a key turning point in the history of the Klingon Empire and Worf's place in it.
On the verge of being confirmed as the Chancellor of the Empire, Gowron struggled find support among his peers. Lursa and B'Etor, the sisters of the late Duras, were challenging Gowron for his position. As women, they could not become Chancellor but they brought Toral, a young man claiming to be the son of Duras. As the male leader of the House of Duras, he had a claim to the position of Chancellor.
With a civil war on the horizon, Worf and Kurn, who had just revealed his true heritage, offered Gowron ships and troops in exchange for the return of their family's honor. Outraged by the plan that cost the House of Mogh everything, Gowron acquiesced. Unbeknownst to them, the Duras Sisters had forged a secret alliance of their own with the Romulans through the half human, half Romulan child of Tasha Yar.
That's a whole different story.
While the Federation could not get directly involved with the Klingon civil war, they could try and stop the Romulans from funnelling aide to the House of Duras. The Federation task force was successful in cutting off the supply train, leaving Lursa and B'Etor to fend for themselves. The House of Duras fell, leaving Gowron unchallenged and in control of the Klingon Empire.
Once again, Worf changed the direction of the Empire, crippling the nefarious Duras family. That being said, he probably should have killed Toral as he showed up again as an adult to torment Worf on Deep Space Nine.