Ask "who would win" about two characters from the same story and there's often a real answer — they've already fought, or the story's internal rules make the outcome fairly clear. Ask it about two characters who have never met, from franchises with no shared canon, no shared physics, and no author who ever intended them to interact — and you get a crossover battle: the single most argued-about category of "who would win" question on the internet.
A same-universe fight can be settled by pointing at what actually happened in the story. A crossover has nothing to point at. Every verdict has to be built from scratch: take what each character has actually shown (their real feats, not just fan hype), place both on some kind of comparable scale, and reason through what happens when their very different rule sets collide. There's no canon answer waiting to be looked up — which is exactly why crossover threads run for years on r/whowouldwin and fill entire wikis with scaling arguments. See the Power Scaling Guide for how that feats-vs-hype reasoning actually works.
The oldest crossover rivalry on the internet. Marvel and DC were never going to let their flagship characters actually meet in canon at any real scale, so fans have been running the matchup themselves for decades. It's also the category with the clearest power tiers, since both universes publish extremely detailed official strength scales — which makes the debates sharper, not softer.
Within one anime series, power levels are usually explicit. Cross-series is where it gets contentious — a Shonen protagonist from one franchise against the strongest character from a completely different one, with wildly different in-universe physics (ki-based power vs. cursed energy vs. Devil Fruit abilities). This is consistently APEX Versus's single most-searched and most-cited comparison category.
Game protagonists rarely get compared within their own franchise (there's usually only one), so nearly every "who would win" question about them is already a crossover by default — against another game's hero, or against a movie/anime character entirely.
APEX Versus doesn't try to convert everything to one universal power number. It classifies each character into the right category first (anime, movie, video game, mythology, and eleven others), scores them on that category's own specific dimensions, and only then compares the two results — the same principle described in full on the Methodology page. A crossover verdict is still an estimate, exactly like a human fan's would be, but it's built from a consistent process applied the same way every time, not a one-off gut call.
Worth remembering: a crossover verdict — from a person or an AI — is never a documented fact, because the fight never happened. It's the most informed estimate available, built from what each side has actually shown.