The might Abaddon.
Hi also brings his apprentice, a Chaos Lord in terminator armor.
In my last game, I had the chance to field my Chaos Lord in terminator armor (mark of Nurgle, blight grenades, burning brand and power sword). He and his Chosen unit charged Belial and his Deathwing knights unit in the first turn. I called a challenge with my Chaos Lord, and Belial accepted. All the Chosen got only one knight killed before being obliterated by the knights. However, the challenge lasted until the end of the game, with only one Wound take by Belial.