Fan Made Death Battle Trailer Shadow Vs Vincent Valentine(Sonic Vs Final Fantasy)Remake
Both are edgy, gun-wielding antiheroes with a black and red color scheme, transformations and mysterious pasts.
Because of the experiments of a crazy scientist, both of these characters are empowered by Chaos because of powerful gemstones they have a link to. These experiments were done so that they could become ultimate lifeforms.
Their stories involve a loved one (who is also an ancestor to the main villain) who suffered from an illness. After losing said person, they are sealed away for many, many years until being awoken from slumber and joining a team in order to seek revenge, and eventually to save the planet from a giant object crashing into it (set on course by series respective gemstones).
Due to their high popularity among fans, they received respective spin-off games that used shooter mechanics for the first time in their series. They are immortal, wield multiple gemstones to use various abilities (including time stop, energy projectiles and an all-powerful explosion), and have flashbacks about their pasts.