It's best 99% of the time, but not 100%.
You're in multiple threads with nonsense like this, @StephenIGuess. Are you a ten-yr-old? Stop, please.
I believe this puzzle speaks for itself.
White to move. Mate in 2.
See also:
Same thing. Mate in 2.
And this one. White to move and win.
A simple example... in this position, promotion to a Knight wins the opponent's Queen.
Well sometimes you need to under promote to a rook,night or bishop to prevent stalemate some times , but I do it to annoy my opponent.
These puzzles are easy