Disclaimer: I don't own Harry Potter. (At least, not the last time I checked.) But I do own my brain, my rhymes, and my Scholastic Rhyming Dictionary. This poem is supposed to be Harry's thoughts when he realizes exactly what the prophecy means. Spoilers through OotP (sort of).
No Other Way
Murder or be murdered;
There is no other way.
I will be killed or be a killer,
No matter what others say.
They might say that it's my destiny,
You can't escape your fate,
It doesn't matter what I think;
It's already too late.
Either I will kill the Dark Lord,
Or he will do me in.
No matter how you look at it,
There's no way I can win.
So I will perform my duty
And will kill him if I can,
Even if it's just to stop him
From killing off another man.
I don't wish to be a slayer,
But I cannot bear to see
Voldemort kill another loved one
Just to get at me.
For the sake of all my friends
I will carry this plan through
Though it means I'll be a killer,
There's nothing else to do.
I know that this must be done,
But still I will rue the day
When I murder or am murdered
Because there is no other way.