Inquisitor

A historical figure who was part of the Inquisition, a religious institution that persecuted and punished heretics and dissenters in the Catholic Church.
An Inquisitor was usually a priest or a monk who had judicial or investigative powers to interrogate, torture, or execute those accused of heresy.
Some of the most notorious Inquisitors were Tomás de Torquemada, who led the Spanish Inquisition, and Heinrich Institoris, who wrote the Malleus Maleficarum, a manual for witch-hunters.

A fictional character who is a dark side agent of the Galactic Empire in the Star Wars universe.
An Inquisitor was a former Jedi who turned to the dark side and served Darth Vader and the Emperor.
Their main mission was to hunt down and eliminate the surviving Jedi and other Force-sensitive individuals.
They wielded double-bladed lightsabers and had various Force abilities.
Some of the known Inquisitors were the Grand Inquisitor, the Seventh Sister, and the Ninth Sister.

A generic term for someone who is very harsh, severe, or hostile in making an inquiry or investigation.
An Inquisitor may be motivated by curiosity, suspicion, or malice.
They may ask intrusive or aggressive questions, or use threats or violence to get answers.
An example of an Inquisitor in this sense is Konrad von Marburg, a medieval German priest who was notorious for his brutal methods of interrogating heretics and witches.
Depending on which meaning of Inquisitor you have in mind, they may look very different.