Why is evil a problem?

This question refers to arguments about the existence of God. The God we normally think about in the west is supposed to have several characteristics. He is:

Omnipotent (all-powerful)

Omnibenevolent (all-loving)

Omniscient (all-knowing)

However, it is easy to observe that there is much evil in the world. how can a god who has all the trait above allow evil to flourish in the world? This is called the 'inconsistent triad'. Innocent people die in earthquakes, does this mean he does not love them? Or he does not have the power to stop the erathquake? Or he does not know about the earthquake? 

Whichever way you look at it, one of his characteristics must always be compromised due to the problem of evil.

This is one of the strongest arguments used by many to suggest that God does not exist. 

However, there are also many counter arguments. For example, many argue that we cannot understand God as he is far greater than us, he 'acts in mysterious ways' but we must accept there is a reason. Another argument is that it does not disprove God entirely, just the God of the Bible. 

Whether or not you like this argument, it is a very central one in the debate over the existence of God.