Here's how a band of unlikely heroes defeated Vecna and save the Forgotten Realm
Chosen Knights of Korne are no joke. Not uncommon for 5x of them to be 75% of an army's points alongside the BSB and general. Then they absolutely steamroll everything in front of them.
I haven't played against them yet in Old World. I just remember how I used Vaul's Unmaking to wipe out their magic standard back in 6th. Edition only for them to still wipe out multiple units of elves.