Who is Count Olaf / Detective Dupin from The Vile Village and what is their importance?

Count Olaf / Detective Dupin is the villain of the Series of Unfortunate Events novels. Olaf is described as elderly and thin, with a unibrow, wheezing voice, and an eye tattoo on his left ankle. Under the disguise of Detective Dupin, Olaf wears large sunglasses to hide his eyebrow and huge plastic shoes to cover up his tattoo. Olaf is an evil man first entrusted with the Baudelaire children after their parents' deaths. He proved to be a horrific guardian, only interested in the fortune the Baudelaires left behind. Throughout the series, he doggedly chases the Baudelaire children with a series of heinous attempts to get his hands on the children's inheritance.