By half, I really mean, more like one third of it.
I had two lines of one verse worked out, but forgot what they were, other than the second line ended with the title of the song: Villain.
I did work out the chorus and the bridge, though.
This was, more or less, conceived as an original song that I'd use in Red Hood Rider, as something the band The Riders (as in, the members of it) would sing. Them being superheroes, they have a fairly good understanding of how the minds of their rogues work, and the song is meant to cover basically the VAST majority of every villain character ever, briefly lamenting their villainous ways.
The chorus goes:
I used to be a sweet kid,
What happened to me?
All the things I did,
All of the things I've seen.
Swore I'd never grow up,
I'd always be free,
It was never enough,
Thus corrupting.
And the bridge goes:
Was it love,
Was it greed,
Was it vanity?
Was it rage,
Was it need,
What happened to me?
...But that's as far as I got.