T.O.D.
Sort of a difficult question.
Since I've written 11 one-person plays, do they count as monologues?
If so, I'd have to pick (Carole) LOMBARD or YVONNE DE CARLO.
Beyond that, I'd have to go with some of Tennessee Williams' monologues: "Big Daddy" in CAT ON A HOT TIN ROOF, "Catherine" in SUDDENLY, LAST SUMMER....