Twilight's death would cause a ripple effect throughout Equestria. Spike, her loyal assistant, would be completely lost. He would struggle to find his place without Twilight. The Cutie Mark Crusaders, who often looked up to Twilight for guidance, would be devastated. They might even lose their sense of purpose in their quest for cutie marks, as Twilight was always there to encourage and advise them.
The death of Rarity would deeply sadden Twilight. They are good friends and Twilight would feel like she has lost a part of her support system. She might become more withdrawn as she tries to come to terms with the loss.
For Sasuke, if he had a relationship with a female Naruto, her death would be a huge blow. He might become more reclusive and angry, blaming himself or others for not being able to protect her. He could even go on a quest for vengeance against those he deems responsible.
For Hermione, it would be a huge blow. She would likely feel a great sense of guilt, thinking she could have done more to prevent it. She might become more withdrawn and throw herself into her studies even more, but also be haunted by memories of Harry. Ron would be devastated too. He might lose his sense of humor for a while and become more serious. He would also be very angry, perhaps vowing revenge if Harry was killed by someone.
For Weiss, Ruby's death could shatter her sense of hope. Ruby was always the one who seemed to bring light and optimism to the group. Without her, Weiss might become more cynical and withdrawn. She may also question the purpose of their fight.
The other characters would be deeply shaken. For Hermione's friends like Luna, she would be there to comfort Hermione but also be in awe of Draco's selflessness. Neville might be inspired by Draco's act and start to believe that people can change more than he thought. Draco's death would also send ripples through the Slytherin house. Some might be ashamed of how they had treated Draco before, while others might try to carry on his new - found heroism. As for Hermione herself, she would be forever changed. She would become more determined to fight for good in Draco's memory and might even become a bit more withdrawn as she copes with the loss.
It could make them more determined. For example, his comrades might become more resolute in their fight against the enemy, vowing to win in Jerome's memory.
For Stefan, Elena's death could be a huge blow. He might go into a deep depression or spiral out of control as he had always been so in love with her. Damon, too, would be severely affected. He might become even more vengeful and angry, blaming himself or others for her death.
One scenario could be Twilight sacrificing herself to save Equestria from a powerful dark magic. Maybe she has to use all her magic to seal away an ancient evil, and in the process, it drains her life force. Another could be Twilight getting caught in a crossfire between warring factions in Equestria. Since she is a princess and would try to broker peace, she might be targeted by those who don't want peace to prevail.
Emma would be devastated. She and Regina had come a long way from being enemies to friends. Regina's death could make Emma question her own abilities as a savior. She might become more withdrawn at first, but then use her pain to fuel her determination to protect the town even more fiercely, knowing that Regina would have wanted it that way.
If there are rivals in the love story, the boy's death can have different effects. Some rivals may feel a strange sense of remorse, even if they were competing for the girl's love. Others may see it as an opportunity, but this often comes with a heavy burden of guilt. The death of the boy can also inspire other characters to be more open about their feelings or to cherish the people they love more, as they have witnessed the tragic consequences of unspoken or unfulfilled love.