One scenario could be that she sacrifices herself to save the world from a powerful alien threat. She might make a last - stand alone, knowing that she has no chance of survival but doing it anyway to protect the Earth and her friends. Another could be that she is betrayed by someone she trusts deeply within the Avengers, and this betrayal leads to her death.
In a more complex scenario, she could be caught in a time - loop where she keeps reliving her death in different ways. Each time she tries to change the outcome, but it always ends the same. Eventually, she accepts her fate, and her death becomes a catalyst for the other Avengers to come together and find a way to break the loop and avenge her.
One scenario could be Gon sacrificing himself to save Killua from a powerful enemy. He might jump in front of a deadly attack, knowing full well it would cost him his life. His last words to Killua could be about their friendship and how he's glad they had their adventures together.
One scenario could be Lupin sacrificing himself during a major battle against the Death Eaters. He might use his werewolf form to his advantage, taking on multiple enemies at once but getting fatally injured in the process. His last moments could be spent looking at Harry, seeing the hope for a better future in his eyes.
One possible scenario could be that Harry loses the love of his life. Maybe she was killed in a battle against dark forces, and he is unable to move on from that grief. His broken heart then leads to his own death as he slowly loses the will to live, consumed by his sorrow and memories of her.
One possible scenario could be Deidara getting seriously injured during a battle with a powerful enemy. Maybe he underestimates his opponent and ends up with life - threatening wounds. His comrades might be too far away to help immediately, leaving him to struggle alone.
One scenario could be Hiccup getting seriously injured during a dragon fight. Maybe he's protecting Toothless and takes a direct hit from another dragon's attack. This could lead to a story of his slow recovery, with his friends and family rallying around him.
One interesting scenario could be them teaming up for a stealth mission. Spider - Man's agility and Black Widow's combat skills would make them a formidable duo. They could be sneaking around an enemy base, with Spider - Man using his webs to silently take out guards from above while Black Widow uses her martial arts to take down any threats on the ground.
Another situation could be that they are on a mission to rescue some hostages. The enemy has set up a complex ambush. Sasuke is hit by a barrage of shuriken and kunai, getting multiple cuts and bruises. Sakura tries to heal him but is then attacked herself. She gets a head injury which affects her ability to use her medical jutsu effectively, leaving them both in a very vulnerable state.
One scenario could be Naruto being forced to choose between the safety of the village and Boruto's life in a dangerous situation. Maybe he has to send Boruto on a near - impossible mission for the greater good, which really hurts Boruto as he feels abandoned by his father. Another could be Naruto being under a genjutsu and unknowingly attacking Boruto, causing physical and emotional harm.
One scenario could be Minho getting seriously injured during a dangerous maze run. Maybe he gets attacked by a griever and sustains deep wounds. His friends would then be in a panic, trying to get him back to safety while also fearing the worst for him.
Another possibility is that Troy is hurt in an accident outside of his Power Ranger duties. This forces him to deal with his vulnerability and the fear that he might not be able to return to his role as a Power Ranger. His friends then have to support him through his recovery both physically and mentally.