White's ko threat was an utter failure. If you push into a knight's move as a ko threat the obvious and correct in most cases follow up is to push through breaking the opponent's shape:
- Click Here To Show Diagram Code
[go]$$Bcm51
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . O . . . . . |
$$ | . . O . . X . . . . . X . O . O O . . |
$$ | . . . O . . . . X , . . . . X X X . . |
$$ | . . . . . O . . . . . . X . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . O X O . . . . . . . . . . |
$$ | . . . , . . X 1 X O . . O . . X . . . |
$$ | . . . . . . O X O . . . . . . . . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . 3 . . . |
$$ | . . . . . O X . . . . . . . . . . . . |
$$ | . . . . . O X . . . . . X 2 . . . . . |
$$ | . . . O . O X . . , . . . O X X X . . |
$$ | . . . O X X . . . . . X . O . O O . . |
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
If you think black just answers at 53 and you didn't do enough then your ko threat was bad (and if you didn't have better threats you shouldn't have played the ko).
If you don't push through the move you play needs to be able to do something awesome if black does then play the obvious move of blocking. One idea is be in the right place to help the cut:
- Click Here To Show Diagram Code
[go]$$Bcm51
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . O . . . . . |
$$ | . . O . . X . . . . . X . O . O O . . |
$$ | . . . O . . . . X , . . . . X X X . . |
$$ | . . . . . O . . . . . . X . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . O X O . . . . . . . . . . |
$$ | . . . , . . X 1 X O . . O . . X . . . |
$$ | . . . . . . O X O . . . . . . . . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . O X . . . . . . . 2 . 5 . . |
$$ | . . . . . O X . . . . . X 3 4 . . . . |
$$ | . . . O . O X . . , . . . O X X X . . |
$$ | . . . O X X . . . . . X . O . O O . . |
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
but then black can play 55 and isn't dead and can reasonably fight so that's a failure too.