Too Late Luigi

he is an evil and sadistic spirit who tortures others after his death simply to vent his frustration.

A notable trait that Luigi has is his hatred towards his older brother, Mario, for killing him and wants to make him pay. He does this by relentlessly torturing him throughout various levels created by him before ultimately killing him in the same area where he once died. It's unknown if Luigi was aware that Mario did not mean to kill him (as evidenced by him having a look of deep remorse and depression) or simply did not care.

He is also an incredibly dark creature that will reference things that are terrifying at will. It also isn't transparent, but it does still just look like a tall Luigi.