Inferno’s main forces.

On Veteran difficulty, you simply won't have enough resources to build up, hire a large number of heroes, and buy all the available upgrades. And it's unlikely you'll be able to defend your resources without any losses, especially if there are any Mages or Druids involved. You'll also have to choose between Tilseck and Haghesh – you can only develop one of them. Meanwhile, Udaleb has an easy start with Chaos elementals, jumpers, hounds, and a ballista. Although, even there, it's unlikely you'll avoid losses.