>>23533455
Demonbane. It actually got a lot of love in UX. Pretty big plot importance, good interactions with the rest of the cast, really good as a unit and kept getting upgraded throughout the game so it got pretty much all of its attacks from the source material, nice animations, playable Master Therion. Hell, Ruri even kept her pantyshot cut-in which definitely wouldn't fly these days.
By debuting and being stuck on a handheld is still kind of disappointing. Every time a new SRW is announced I keep hoping to see it on the cast list. They even make a direct reference to the sequel in UX so there's still plenty of plot to add if they ever bring it back.