I've stood in hell
Where many had to suffer
I stared the devil in the eyes
In this part, Avenged Sevenfold is refering to the time when they visited Iraq when they were gonna play for US troops back in 2011. "I stared the devil in the eye" makes reference when they looked at a picture of Saddam Hussein in his abandonded palace.
Taken from: http://www.avengedsevenfold.com/news/kerrangs-150-secrets-behind-the-songs-avenged-sevenfolds-coming-home