Well, 'Ultraman' could be one. It features powerful heroes defending against threats and has action-packed scenes similar to Power Rangers. Also, the concept of having a team of heroes working together is common in both.
I'd suggest 'One-Punch Man'. Both have characters with extraordinary powers and a sense of justice. However, the tone and style might be a bit different. Superman is more traditional heroic, while One-Punch Man has a comedic twist.
I think there are a few. For example, some historical or mythological manga might share similar elements. But it really depends on your specific expectations.
I think 'Ouran High School Host Club' could be similar. It has a light-hearted and comedic tone with diverse and charming characters like in 'Fruits Basket'.
It's moderately popular. There's a decent fan base for it, especially among fans of the Power Rangers franchise.
You might like 'Jujutsu Kaisen'. It has a similar theme of students learning and mastering their powers, along with a diverse range of personalities among the characters, much like in MHA.
Personally, I'd suggest Hunter x Hunter. It shares the elements of fantasy, adventure, and character development that are common in Fairy Tail and One Piece. The depth of the world-building and the complexity of the characters make it comparable.
One common theme is the discovery of new powers. For example, a ranger might find a hidden power within themselves or a new power source. Another theme is the fight against new and powerful villains. Fanfics often introduce villains that are even more menacing than the ones in the original series.
The leader of the Dark Rangers is often a popular character. They usually have strong leadership skills and powerful dark abilities. For example, a character who can control shadows and use them to attack or defend.
I'd suggest 'Clannad'. It shares elements of heartfelt storytelling and explores various emotions, similar to what you find in 'The Promise'. There are touching moments and character arcs that might strike a chord if you enjoyed 'The Promise'.
Well, 'The Vampire Diaries' manga could be comparable. It shares the theme of vampire love and drama that Twilight is known for. Also, the character dynamics and emotional conflicts have some similarities.