In International Draughts the king is long without any restriction. In Thai Checkers the king must stop on the first vacant square after a captured piece. Killer Draughts relaxes the restriction: the king must stop on the first vacant square after the last captured piece, if and only if that piece is also a king.

The rule is specifically tailored to capture a king with two kings in International Draughts, with an as minimal as possible rulechange. In the diagram there's no escape for the black king.

It almost certainly would have the required effect of less draws in high level matchplay, but everything that these very players contributed to the game in terms of theory would be affected. So it is unlikely that those for whom the rule was intended, would abide by it.

Moreover, the rule retains the smell of a band aid. Square games like Turkish, Croda or Dameo don't need an extra rule to capture a lone king with two kings.

Using the Killer Draughts applet