See also what I said about how
being the last character makes you the dream crusher, yada yada... same story as Incineroar, really. Though I find it funny that Corrin gets the hate usually associated with being the last character when Bayonetta was actually the last one for
Smash 4's DLC. I think in Corrin's case, he got it especially bad due to perceived
Fire Emblem overrepresentation, while Bayonetta got more of a free pass due to being from a new franchise. Come to think of it, the "overrepresentation" angle also probably explains some of Incineroar's hatedom.
Also, was R.O.B.'s backlash really
that bad? He got a few remarks about "not actually being a character", but I thought most people were too wowed by the Subspace Emissary twist he was the core of, as well as the "awesome robot flying and shooting lasers" angle, to be mad about R.O.B. I recall Toon Link and Wolf (the actual last characters for
Brawl) getting worse vitriol for being semi-clones and snubbing more "deserving" reps from their series such as Midna, Tingle, Vaati, and Krystal... though maybe I'm projecting a bit, and in any case, people didn't go as ballistic on them as they did on Corrin or Incineroar.