Fiora's lore is almost identical to Darius' lore.

Fiora

"''I have come to kill you for the sake of honor. And though you possess none, you will die just the same.'' The most feared duelist in all of Valoran, Fiora is as renowned for her indomitable will and haughty pride as she is for her skill with the blade. She was born to Demacia's House Laurent, a once-proud family whose reputation was tarnished by the actions of her father. In an unprecedented move, Fiora challenged him to single combat and, upon winning, took control of House Laurent. Defying the Demacian establishment, she has set about restoring the reputation and pride of her family name, one duel at a time."

Darius

There is no greater symbol of Noxian might than Darius, the nation's most feared and battle-hardened warrior. Orphaned at a young age, Darius had to fight to keep himself and his DravenSquare.png younger brother alive. By the time he joined the military, he had already developed the strength and discipline of a veteran soldier. The first true test of Darius' resolve occurred in a crucial battle against Demacia, where the Noxian forces were exhausted and outnumbered. Darius' captain called for his troops to retreat, but Darius refused to accept such an act of cowardice. Breaking formation, Darius strode towards the captain and decapitated him with one sweep of his gigantic axe. Both terrified and inspired, the soldiers followed Darius into battle and fought with incredible strength and fervor. After a long and grueling battle, they ultimately emerged victorious. Seizing momentum from this victory, Darius led his now fiercely loyal troops in a devastating campaign against Demacia. After proving his power on the battlefield, Darius turned his gaze homeward. He saw a Noxus riddled with weakness, where greedy, complacent nobles drained the nation's strength. Seeking to restore his country to greatness, Darius took it upon himself to reshape the Noxian leadership. He identified weak figureheads and violently removed them from their positions of power. Many in Noxus saw Darius' cull as an attempt to seize power, but he had a different plan for the throne. He had been watching the rise of Jericho Swain with keen interest. In Swain, Darius saw a leader with the mind and determination to bring Noxus to glory. Now allied with the Master Tactician, Darius works to unite the nation behind his vision of true Noxian strength.

Both Darius and Fiora disregarded their orders/traditions to kill a superior who proved to be an honorless coward, and used that moment to launch themselves into a position of power, where they could violently purge the weakness and corruption from what they consider to be the most important thing in the world.

I hope to one day see some actual lore about this, since they're both taking an extremely similar route towards making their homes stronger. Perhaps even some measure of grudging respect between the two, since, despite the fact that their nations are at war, they both have identical goals and methods. Or, perhaps, they would see each other as great threats, since each represents the greatest chance for their enemy to become stronger.