Newport RI cops call their "bad guys", NITWITS'I do believe that "Polly Vaughn" is another version of "Molly Bawn", supposedly the oldest known European Ballad.
If you want a really gory one, where everyone of the principals die, try "Lord Thomas and Fair Ellender" Note: The Brown girl was not African, she was just not Fair like Ellender.so here goes (if I can remember it all)

Father dear father come riddle me this
Come riddle it all as one.
Whether to marry Fair Ellender
Or to bring the brown girl home.

The Brown Girl she has house and land
Fair Ellender she has none
I charge you with my blessings, son
To bring the brown girl home

He rode 'till he came to Fair Ellender's door
So lightly taped at the ring
I've come to invite you to my wedding
said she 'tis a sorrowful thing

Fair Ellender dressed in silks so fine
Her maidens, all in green
Every town that they rode through
They took her to be some queen

She rode 'till she came to Lord Thomas's door
So lightly tapped at the ring
Warm was her welcome there
Lord Thomas' welcoming.

Then taking her by her lilly white hand
He led her her cross'd the hall.
Sitting her down at the table's head
Above his bride and all

The Brown girl took out a little Pen Knife
It was both keen and small
With it she pierced Fair Ellender's breast
"twixt the short ribs and the tall

Lord Thomas asked Fair Ellender
Why do you look sop pale?
You used to have such red rosy cheeks
As ever shone through a vail

Oh are you blind and cannot you see
Your bride has murdered me
I think I feel my own life's blood
come trickling down on me.

Lord Thomas's sword was by his side,
It was both keen and small.
With it he cut off the brown girls head
And stove it against the wall

then olkacing the sword all on the floor
The point against his breast
saying this is the end of three young loves
God send their souls to rest

Father dear father come dig my grave
dig it both loing and deep
Bury Fair Ellender in my arms
The brown girl at my feet.