>Elizabeth Bathory
The usual story is that she tortured and killed 300 (Slovak - ofc) peasant girls, testimonies of witnesses prove that.
The matter of fact is there are 303+4 testimonies recorded, this is where the number comes from. However the 303 is entirely useless. About 2/3 knew nothing incriminating, the rest is hearsay.
The +4 is 4 people from her court, basically her closest servants, 3 women and a man. They told about torture and death of 4 or 5 girls (young adult women). Torture including beating with a stick, burning hands with hot coins, dipping on icy water and such. They also told about funerals. However their testimony was forced by torture, and while they could have been crown witnesses, they were executed before any court hearing.
The countess was never sentenced, she died after four years of house arrest, way after any official procedure took place.
"Some argue" that some of the "torture" was efforts to cure illnesses (like treating high temperature with cold water). Some also mentions that certain deaths were due to epidemic.
Fun thing: when "Good ol' Erzse" was arrested (this event was actually an unlawful act, nobles had certain rights) there were two servant girls in the dungeon - they were never heard out, noone asked for their testimony.