In The Crucible by Arthur Miller, what characters abuse their power and what are examples of this from the text?

Abigail Williams certainly abuses her power.  Once she realizes, at the end of Act One, how powerful an accuser can be, she seizes that role, repeating the accusations Tituba has already made and adding four more of her own in mere moments.  Then, just two weeks later, when Mary Warren returns to the Proctors' from a day in court, she informs John and Elizabeth that there are now thirty-nine accused.  Clearly, then, Abigail is abusing the power granted to her by the courts, especially because she told John that Betty Parris's illness "had naught to do with witchcraft," and that is what began this whole sham.  Moreover, Abigail accuses Elizabeth of sending out her "familiar spirit" to push a needle into Abigail's stomach after she saw Mary Warren place the needle into a poppet's stomach for safekeeping.  Abigail has tried to frame Elizabeth, and she is ultimately successful when Elizabeth is convicted.

Giles Corey presents some evidence which suggests that Thomas Putnam is abusing his power as the father of one of the accusers.  Giles says that "an honest man" heard Putnam say that "The day his daughter [accused] [George] Jacobs, he said she'd given him a fair gift of land."  It begins to sound as if Putnam put his daughter up to accusing Jacobs so that Jacobs's extensive property would go up for auction when he's convicted.  As Giles says, only Putnam has "the coin to buy so great a piece."

Deputy Governor Danforth also abuses his power when he refuses to call off or defer the hangings that take place in Act Four.  Despite Abigail's theft and flight, and despite the fact that the town is near rebellion over the obvious wrongness of the trials, Danforth is implacable.  He says, "Postponement now speaks a foundering on my part; reprieve or pardon must cast doubt upon the guilt of them that died till now."  He is more concerned about retaining his power than he is about unearthing the truth.  Danforth would rather hang innocent people than undermine his own or the court's authority.  This is certainly an abuse of his power.