What is the meaning of Genesis 4:15?

* The two F.O.G. Bibles & Commentary below are currently a work in progress.

“Not so!” replied the LORD. “If anyone slays Cain, then Cain will be avenged sevenfold.” And the LORD placed a mark on Cain, so that no one who found him would kill him.

Berean Standard Bible (BSB)

Yahweh said to him, “Therefore whoever slays Cain, vengeance will be taken on him sevenfold.” Yahweh appointed a sign for Cain, lest any finding him should strike him.

World English Bible (WEB)

And the LORD{H3068} said{H559}{(H8799)} unto him, Therefore{H3651} whosoever slayeth{H2026}{(H8802)} Cain{H7014}, vengeance shall be taken{H5358}{(H8714)} on him sevenfold{H7659}. And the LORD{H3068} set{H7760}{(H8799)} a mark{H226} upon Cain{H7014}, lest{H1115} any finding{H4672}{(H8802)} him should kill{H5221}{(H8687)} him.

Strong's King James

So יהוה Yahweh spoke to him, "Assuredly, anyone killing Kayin, sevenfold vengeance will be taken!" Then יהוה Yahweh set a sign on Kayin so that nobody, whosoever finding him would strike him.

The F.O.G*

The F.O.G Paraphrase

And Jehovah saith to him, ‘Therefore—of any slayer of Cain sevenfold it is required;’ and Jehovah setteth to Cain a token that none finding him doth slay him.

Young's Literal Translation