'Bitterly' in the Bible

“Then I will pour out a spirit of grace and prayer on the house of David and the residents of Jerusalem, and they will look at Me whom they pierced. They will mourn for Him as one mourns for an only child and weep bitterly for Him as one weeps for a firstborn.

Then they will mourn for him, as for an only son. They will grieve bitterly for him, as for a firstborn son. At that time, Jerusalem will mourn deeply, like the mourning about Hadad-rimmon that took place in the plain of Megiddo.