There are 6 scenarios in the Attila the Hun campaign:
1. The scourge of God
2. The Great Ride
3. The Walls of Constantinople
4. A Barbarian Betrothal
5. The Catalaunian Fields
6. The Fall of Rome
Win every scenario of the campaign using the cheat code “i r winner”. Then, to trigger the achievement, win any scenario of any campaign without using cheat codes. The quickest scenario is the 1st scenario of the William Wallace Learning Campaign: Marching and Fighting.