Why not take the easy way out and make them your usual can of exposition and training?
Very few characters actually make it on their own. Even as loners, they had to learn from somewhere. They had to have a teacher, someone to actually teach them to acquire the skills and traits the author arbitrarily assigned to them.
Someone like a magical talking animal. Or a grizzled washed out wizard. Or the city streets themselves.
“We have to retrieve Blue Beetle’s soul from the Phantom Zone and his body from Gorilla City and get Etrigan to stick the two together!”
Ah yes, death. The final answer. The culmination of a gripping battle or a long march. A powerful tool in the writer’s arsenal, meant to create SHOCK and DRAMA. For surely all will be touched by the loss of their loved one, the legacy and memories they leave behind, and all the emotions that come with it.
And then there’s comic book deaths.
As part of my usual target audience, you’re more than likely familiar with the concept. A character ‘dies’ only to come back to life later, sometimes to joyful celebration and other times to rolled eyes. And of course, you know the various ways this happens: clones, robot doubles, magic, time travel, bad/mad science, fight with Death itself, it was a dream, reality gets mixed up, the works. And of course, the classic “The fans/profits demanded it.”
There are plenty of articles to discuss this particular trope’s merits and faults, both from a literary and in-universe perspective, but I won’t be going into those. Instead, I’ll do my best to present the usual ways this plays out, and hopefully give you some fun and some tips about writing along the way. Because really, discipline aside, it IS important to have fun with writing.