One key element is the initial conflict. There has to be a strong reason for the two to be enemies at first, like a personal grudge or competing goals.
One possibility for the 'Best of Enemies' back story is that they had a shared past with a third party. This third person might have pitted them against each other, either intentionally or unintentionally. Say this person favored one over the other, and the unfavored one developed resentment towards the favored one, starting the enmity.
The 'Best of Enemies' back story might involve a complex relationship between two characters. It could be that they started as rivals in a competitive field, like business or sports. For example, they might have been competing for the same promotion or championship. Their rivalry could have been fueled by jealousy, different ideologies, or personal pride.
Conflict is a key element. There has to be a reason for them to be enemies, like different goals or misunderstandings. For example, in the story of Romeo and Juliet, their families' feud made them enemies at first. Another element is character growth. They need to change their initial views of each other. Also, shared experiences play a big role. Through going through things together, they start to see the good in each other, just as Harry and Hermione in 'Harry Potter' series had many shared adventures that made them closer friends, and if it was a love story, it could be the basis for enemies to lovers.
One key element is the wealthy setting. The 90210 zip code represents luxury. Another is the high - school aspect. The characters' experiences in school, like cliques and popularity contests. Also, relationships play a big part. There were romances and break - ups among the characters.
One key element is the nuclear apocalypse that destroyed Earth. Another is the Ark, the space station where the survivors were living. And of course, the 100 delinquents being sent to Earth.
One key element is the different races. Their relationships and power dynamics play a big role. Another is the political situation, with various kingdoms and factions. Magic is also a key, as it affects battles and the balance of power.
One key element is its evolution from Gastly and Haunter. Another is its connection to shadows and darkness. Also, its mischievous nature is important.
The key elements are the Smurfs themselves, their forest village, and Gargamel. The Smurfs' unique characteristics and their village setting are important parts of the back story, and Gargamel as the main villain.
If it's Guts from 'Berserk', one key element is his origin from a hanged corpse, which sets him apart and makes his existence somewhat of an outcast from the start. Another is his time as a mercenary, where he learned combat skills and survival tactics in a harsh world.
One key element is his desire for power. Bowser wants to rule the Mushroom Kingdom. Another is his rivalry with Mario. Their battles are a big part of his story. Also, his relationship with Princess Peach, as he constantly tries to kidnap her. His army of minions is also an important part of his back story as they help him in his evil plans.