Well, 'Heavenly Bond' is also a good one. It has a unique take on the angel x reader concept. The descriptions of the angel's world and how the reader - character fits into it are really well - done, and the story is full of heartwarming moments.
I'd recommend 'Angel's Devotion'. In this fanfiction, the descriptions of the angel are so vivid, like you can almost see the celestial being in front of you. The way the story unfolds between the angel and the reader is full of mystery and a touch of magic.
Another way is to explore the angel's powers and how they use them in the context of the story. If they have the power of flight, they might use it to save the lost boys from danger. But at the same time, using their powers too much might attract unwanted attention from both the human and celestial worlds. This internal conflict can help to develop the angel reader as a multi - faceted character.
One common theme is love and sacrifice. Since their relationship in the show is complex and full of obstacles, many fanfictions explore how much they are willing to sacrifice for each other. For example, Angel's struggle with his vampire nature and Buffy's duty as the Slayer often lead to situations where they have to make difficult choices for the sake of their love.
One common theme is the exploration of their unspoken feelings. In the show, their relationship was complex, and fanfiction often delves deeper into those emotions that were hinted at but not fully explored. For example, how they might deal with jealousy when one of them is interested in someone else.
One common theme is the exploration of their complex relationship. Given their history of rivalry and shared vampiric nature, many fanfictions dig deep into how they interact with and feel about each other.
Another theme is loyalty. Despite their differences and occasional rivalries, they are often shown to be loyal to each other in fanfictions. For example, in many stories, they will go to great lengths to protect one another.
Redemption is often seen. The demon may be seeking redemption through the love of the angel or vice versa. Also, the idea of defying fate or the order of things. Since angels and demons are supposed to be on opposing sides, their relationship goes against the natural order in their fictional universes.
Love and friendship are often explored. It could be a slow - burn romance where they overcome obstacles to be together, or a strong platonic bond that helps them through tough times. Another theme could be redemption. Maybe one of them has a troubled past and the other helps them find a new path. For example, if Buster has made mistakes in his past, Angel could be the one to guide him towards a better future.