Have you ever noticed how the words awesome and awful have the same exact root? Yet they mean completely opposite things. Let's analyze...
The root of both words is
awe, a word derived from Old English that means “a feeling of fear or amazement”. That in its own right is contradictory, since we perceive fear as a negative emotion, and amazement as a positive emotion. I will use a word that equally describes both: shock.
The suffix is easy:
-ful means full, and
-some means some. Hence, awful means “fully shocking”, and awesome means “somewhat shocking”.
The philosophy behind awesome and awful is that awe (or in my theory, any emotion) is meaningless without quantity. A little of it is good, and lot of it is bad.