Piper is portrayed as an amoral psychopath who'll not hesitate to destroy anyone she perceives as a threat to her own sinister designs. Like numerous clinically-diagnosed psychopaths, Piper wears a metaphorical mask of normalcy throughout the series, establishing herself as a cool-headed schemer and gaining the trust of those around her, despite her rather untrustworthy physical appearance. Even with this mask, Piper's psychopathic tendencies tend to seep through and become apparent to the viewers.
This also establishes Piper as an emotional sadist, getting a laugh out and treating Emma Duval in an especially harsh manner. Piper also displays narcissistic tendencies, her most obvious ones being her obsessive desire for power and sense of entitlement, as well as manipulating the Sheriff to achieve her atrocious goals.
List of Victims
2) Riley Marra
3) Will Belmont