What does scourge mean in this context

Prince: This letter doth make good the friar's words,
Their course of love, the tidings of her death:
And here he writes that he did buy a poison
of a poor 'pothecary, and therewithal
Came to this vault to die, and lie with Juliet.--
Where be these enemies?--Capulet,--Montague,--
See what a scourge is laid upon your hate,
That Heaven finds means to kill your joys with love!

In this context, "scourge" means a cause of great suffering or punishment. The Prince is referring to the tragic consequences of the feud between the Capulets and Montagues, which has ultimately led to the deaths of Romeo and Juliet. He is highlighting how their hatred has resulted in them losing the thing they hold most dear - their children.