82.

David killed every male in Edom

There's not a lot to go on here, just a few contradictory verses from four different books.

There's a one-verse story from 2 Samuel saying that David got a name for himself by killing 18,000 Syrians in the valley of salt.

David gat him a name when he returned from smiting of the Syrians in the valley of salt, being eighteen thousand men. 2 Samuel 8:13

Then there's a (sort of) similar verse from 1 Chronicles that agrees with 2 Samuel on the number killed (18,000) and the site of the killing (the valley of salt), but disagrees about the identities of the killer (Abishai vs. David) and the people killed (Syrians vs. Edomites).

Abishai ... slew of the Edomites in the valley of salt eighteen thousand. 1 Chronicles 18:12

And there's a Psalm story that says it was Joab who killed 12,000 in the valley of salt with the candlestick (or was it the lead pipe?).

Joab returned, and smote of Edom in the valley of salt twelve thousand. Psalm 60:1

There's something else we are told about this killing. After the 18,000 (or 12,000) Edomites (or Syrians) were killed in the valley of salt by David (or Abishai or Joab), Joab killed every male in Edom.

When David was in Edom, and Joab the captain of the host was gone up to bury the slain, after he had smitten every male in Edom; (For six months did Joab remain there with all Israel, until he had cut off every male in Edom:) 1 Kings 11:15-16

So how many were killed in this killing? 18,000 or 12,000 in the valley of salt? And how many males were killed in Edom in Joab's male genocide?

I'll take 15,000 (the average of 12,000 and 18,000) for the number of Edomite (or Syrian) soldiers that were killed, and guess that 50,000 males of all ages were slaughtered, for a total of 65,000 in all.