Middle-earth: Shadow of Mordor

Monolith's 2014 game is remembered for one system, and deservedly. The Nemesis system generates the orc captains of Sauron's army procedurally, gives them names, strengths, fears and grudges, and then lets them remember you. An orc who kills you is promoted, comes back scarred by whatever you hit him with, and taunts you about it; one who survives your ambush turns up later with a fear of fire he did not have before. Because the hierarchy is a real structure, you can work it - assassinate a warchief's bodyguards, brand a captain and turn him into a mole, then trigger a betrayal mid-fight. The rest is a competent open-world action game built on Arkham's counter-based combat and Assassin's Creed's climbing, with a forgettable story about a ranger sharing a body with an elven wraith. Nobody plays it for the plot. Warner patented the Nemesis system, which is why nothing else has one, and Shadow of War expanded it before burying it under microtransactions that were later removed.