Let me tell you the tail of Lugnug the Stout.
There was once a simple Uruk named Lugnug. He was a simple Orc, and was helping his friend, Mushlug become Warchief in a Caragor hunt. Talion came, intending to kill Mushlug, but Lugnug wouldn't let his friend be killed, and managed to kill Talion, him becoming a captain and gaining the title, the Stout. Lugnug always stayed by his friend's side, acting as a bodyguard, all the while getting stronger by hosting feasts and duels.
Eventually Talion came from Mushlug, sneaking into his base and killing his supporters to draw him out. Lugnug stayed by his friend, till Talion descended upon them, dropping down on Mushlug and killing him in one go. Lugnug was angered by this, and charged at Talion, forcing the ranger to flee, but not before burning Lugnug's face.
Lugnug continued his work, rising in power, longing for the day he'd get to kill Talion, and they would meet again, but this time, the Uruk would not be the victor. He was hoasting a feast, one that could only be assumed was to mourn his friend, when Talion attacked. Their blades met, and Lugnug cursed Talion, revealing the burn marks upon his face. Instead of claiming his vengeance, he was knocked unconscious by Talion, who had cut off his arm and left him for dead.
He visited his friend, by the name of Draza the Blacksmith, having a metal claw put on his arm to replace his hand. He was given good chance to test it, as Talion arrived. Once again, he almost felled Talion, but was delayed when a piece of Caragor bait was dropped, attracting the beasts and allowing Talion to escape.
The game of cat and mouse continued, neither managing to kill the other, but Lugnug getting more wounded, his skin turning pale, scars marking his flesh, and his face getting so badly burned he covered it with a burlap sack. One night, Lugnug was on patrol, killing the Ghuls that attacked him, till Talion came. The pair duelled, exchanging blows and cuts till morning, and only one of them stood. Lugnug, had won, and claimed the title of warchief.
This lead Talion to gain strength, becoming more skilled and learning the ability to brand others. He found both of his nemesis's bodyguards, corrupting them before having one of his warchiefs declare a riot on Lugnug. Talion arrived to see the fight begin, activating his sleeper agents and having them strike their former lord in the back.
Lugnug would not bare this insolence, and he cut his foes down one by one, till only the rival warchief, and one of Lugnug's former bodyguards was left. Talion descended now, with the intention of giving Lugnug the demise he deserved. and this time, he would win. He knocked his rival to the ground, the Uruk declaring he had been a worthy foe, and he would take his death well. Talion struck, decapitating Lugnug and sending his head to the floor.
Yes, the nemesis system is awesome.