Why is the world gone so evil?

Answer: Evil was let into the world due to free will. God gave us the choice to do what we want. He didn't want to control us like robots, because he loves us. This does not mean he won't be there for us, and look after us.

Answer: Balance and free will allows for evil to exist in the world.

The balance allows us as humans to appreciate good for what it is a not take it for granted or something that we are entitled to but have to work for, and so, when we achieve it or come across it, we see it for all it is worth and usually want to spread it amongst others.

Free will allowed by God being a loving being and giving us a choice to be good rather than forcing us under His will to do so allows for us to be evil as well as spread it amongst others.