Questioned said:
It is true that one of the ten commandments "Do not kill". That seems fair, because a loving God would not want his creation to harm each other. But my concern is that if he tells us not to kill, and he loves us, then how could God cause the flood, burn Soddom and Gommarah (forgot how to spell them), and kill several people in the book of Genesis.
I actually considered Satanism because though Satan is evil, he never claimed to be good, nor has he ever killed vast amounts of people. God, on the other hand, has claimed to love and care, yet killed so many people without remorse.
So my question is, how could a loving God do all of this while being God, while Satan does none of this and is "evil".
In fact, does good or evil even exist? Who is the real good being and the evil one?
The others have supplied very good and correct answers to the specifics of your post. But I want to address it generally.
You have rightly said "a loving God." God is indeed, Loving. But he is much more. He is also the Supreme Creator, Ruler, the final Authority, and the Salvation of the universe, and beyond. He is the Father of all that he surveys, and that is very much more than what we can see on or from the earth. As such, he is the creator of Love, but also responsible for Justice and Order. He holds all the reins of power in his hand. The examples of his "killing" that you mentioned above are the implementation of justice and judgment upon evil-doers.
Yet, he is also supremely Merciful. There are many examples of this in the Bible, right along side of the afore mentioned examples of his judgments. Perhaps you are familiar with the story of Jonah, the man who was swallowed by the whale (great fish). The part of the story that often gets overlooked is that God told Jonah to go to Nineveh, a city of great wickedness, and warn them of their impending destruction (in forty days) unless they turned from their wicked ways. After the whale incident, Jonah went and delivered the message. The people of Nineveh heard the message, turned away from their evil ways, and God spared them. But there is a twist at the end of the story: God's mercy on the people of Nineveh displeased Jonah. He was upset that God had uprooted him from his peaceful existence, caused him to go through so much trouble and effort (such as being swallowed by the fish), just to deliver a message when he knew that God would be merciful anyway. "Ah, LORD, was not this what I said when I was still in my country? Therefore I fled previously to Tarshish; for I know that You
are a gracious and merciful God, slow to anger and abundant in lovingkindness, One who relents from doing harm." (Jonah 4:2) So God said to him "Is it right for you to be angry?......"And should I not pity Nineveh, that great city, in which there are more than one hundred and twenty thousand persons...?"
The point is that God is merciful, wants to be merciful, and goes to great lengths to extend mercy. After all, he sent his only Son to die for us so that we may obtain mercy. But, He can only extend His mercy to those who ask for it and repent of their sinful ways. It is only in the face of great evil and rebellion that he is faced with implementing justice through the destruction of the evil-doers.
As for Satan, you are right in assessing his evilness but wrong in your conclusion. Satan is responsible for an untold number of deaths throughout history. He is the author of every evil imagining in the hearts and minds of men that have led them to kill and maim, go to war, enslave, and commit all sorts of atrocities. For example, the holocaust is straight from the mind of Satan. His only goal in this world is to destroy whatever goodness there is.
That he does not is another miracle of God's mercy. God has him on a leash, and he is only allowed to do so much. You will find in the first chapter of Job that God puts a limit on the evil that Satan is allowed to perpetrate on mankind. God has a "restraining order" on Satan, but only for the time being. "For the mystery of lawlessness is already at work; only He who now restrains
will do so until He is taken out of the way." (2 Thes. 2:7)
Your take on this whole deal is from the perspective of one who has little knowledge of the heart and mind of God, and that is why the other posters have suggested that you study the Scriptures. But also, your perception is colored by your unbelief, and you will not fully understand God's ways until you place your faith in Jesus Christ. "But the natural [unsaved*] man does not receive the things of the Spirit of God, for they are foolishness to him; nor can he know
them, because they are spiritually discerned. (1 Cor. 2:14; *- my word)
I hope and pray that you will commit your life to God as you study His Word, and that He will give you understanding.