Vengeful ghosts also differ in that they can summon thunder and, if they're powerful enough, make lightning fall ("Making thunder fall is actually a common ability for vengeful spirits [...] For small vengeful spirits, they can only make a rumbling sound at most, but as their level of resentment increases they can make crackling sounds, and great vengeful spirits can actually cause thunder").
Regarding their creation, Kanako says "Vengeful spirits are a kind of phantom and are basically the same, but a phantom that comes from a human that gave in to malice or carries a strong grudge, and strays from the cycle of reincarnation by remaining a phantom eternally is called a vengeful spirit".
So they come from both bad people ("Humans that are condemned to Hell after death often become vengeful spirits") and people that have strong grudges (like Tojiko; I'd guess her grudge was against Futo for killing her).
It also seems that, although losing their grudge makes them stop being classified as vengeful spirits, they retain their lighting related powers ("Fortunately, her grudge has almost dissipated, and she is turning into an mere thunder-causing ghost")
BTW, Murasa isn't a "vengeful spirit"; she's a "restless spirit", a phantom that could not even cross the Sanzu river because of lingering attachments to the world.
The ghost category will end up having more sub-entries than the whole race list if you take ZUN's full ghost taxonomy into account
