The world, or at least the local part, is quite hostile, maybe decaying, inspired by both the Witcher and Dark Souls.
Harry is in a band of adventurers, or perhaps soldiers, fighting their way through the hostile countryside, fending off wild beasts, monsters, demons, etc.
Their goal is to deliver a message to an elven city, which they finally manage, wounded, ragged, with casualties.
Harry is sent to the temple of their Sun deity (Sarenrae expy, if you know Pathfinder) to recover from something.
One of his healers is Fleur, an elf with an actual celestial ancestry, an aasimar. During his recovery, they get to know each other, and Harry comes to worship the Sun deity too. Harry and Fleur fall in love.
They have some adventures together, becoming quite renowned.
Eventually, they get embroiled in a large conflict, properly apocalyptic, akin to the crusades at the Worldwound in Pathfinder, or perhaps Lastwall. They fight there for a long time, both becoming practically living legends, but also growing increasingly weary, worn down.
During one battle Fleur dies, maybe saving Harry's life?
After that, Harry's fighting methods grow increasingly brutal, he starts caring less about protecting the innocent, and more about exacting vengeance on the enemy.
Even later on, Fleur comes back, as an actual angel of the Sun deity, to help combat the threat.
Then there would be, I don't know how long, a development after the war.
Harry faces the dilemma whether to follow his dead wife, or try as a mortal to marry an angel, or try to find another wife, while also dealing with his own traumas, and with who he had become. During the war, he stopped worshipping the Sun deity, but instead follows another deity, Lord of Vows and Vengeance (Ragathiel expy). One of his worries is that when he dies, even if he is found worthy of ascending to Heavens, he wouldn't be allowed to meet Fleur, since they serve different gods.