What is a "King Maker"?

No, what you are describing is commonly known as a "runaway leader".

A kingmaker is a player, not in the position to win the game himself, who makes a move, or is forced to make a move, that effectively decides who of the other players wins the game.

In my opinion several criteria must be met in order for a move to be a true kingmaking move:

1) The kingmaker is forced to make a move that crowns a winner. He cannot make a move that avoids this.
2) It is clear and obvious to the kingmaker that his move effectively crowns another player as the winner.
3) The kingmaking move doesn't improve the kingmaker's own position.

For example, on his turn Adam must play either a red card or a blue card. If he plays the red card Benjamin wins, if he plays the blue card Christopher wins. Whatever he plays he doesn't improve his own position.

Kingmaking can leave a sour taste in the mouth of the players, because it can feel as if the winner was decided by the whim of a single player, instead of through clever play by the winner.

Other people feel kingmaking is just another form of interaction and the cumulative result of all events that happened in the game so far. One could argue that if Benjamin had played a bit better, he wouldn't have gotten into a situation where he needed Adam to play the right card.

Personally, I try to avoid overt kingmaking situations in my designs, although it's not always possible to design an interactive game in such a way that it will never happen.