Spite isn't that of a Frisk, nor a Chara, nor even a Kris. Spite was a player, whom met misfortune and got roped into the multiverse. After experiencing a great loss, Spite was met with hallucinations of a Gaster they called Doc, whom they communicated with in order to building the Core Reverb*. The Core-Reverb took Spite into the Anti-Void, the space between AUs, where they stayed supposedly for an eternity, collecting little fragments of code on the borders of AUs in order to create a physical form for Doc.
It is said that Spite actively sought out the infinite knowledge of CORE!Frisk for a purpose beyond finding Doc a physical form, one that wasn't finite. CORE!Frisk knew though they had best intentions at heart, ultimately would be affiliated with the wrong side, and denied their request to join the Star Sanses, which sent Spite into a destruction of themselves mentally and the outside world physically, using altered savepoints as a mode of transportation, and their ticket into the Bad Guy Sanses.