Ladybird, Ladybird,
Fly away home,
Your house is on fire,
Your children all gone.
This one is not violent, but may cause violent responses after the 20th+ repetition:
Hickery Dickery Dock
The mouse ran up the clock
The clock struck one
The mouse ran down!
Hickery Dickery Dock
I now a well-known German nursery rhyme of which there are countless versions. And I do mean countless...
My amateur translation, loss of rhythm/rhyme:
Sleep baby sleep,
mother tends the sheep
father is in angel's land
angel's land has burnt down,
sleep baby sleep
or
sleep baby sleep
your father is in war
your mother is in Pomerania
Pomerania has burnt down
sleep baby sleep
or even
sleep baby sleep,
outside stand two sheep,
a black sheep and a white sheep,
and when you fail to sleep,
the black sheep will come to bite you
and the peaceful one:
sleep baby sleep,
your father tends the sheep
your mother juggles the tree
down falls a dream
sleep baby sleep