Bad (A1)
He was a bad friend.
Horrible (A2)
Today was a horrible day: I got low grades in three subject.
Terrible (A2)
That story has a terrible ending: the main character dies in a car accident.
Awful (B1)
I have never eaten such an awful pie.
Dreadful (B2)
Although the weather was dreadful, they were determined to go on a trip.
Appauling (C1)
In spite of global weather changes all over the world, humanity is not able to see the appalling consequences of eccessive use of cars in metropolitan cities.