The God of the Old Testament is Unjust

My opponent said earlier "I disagree because my opponent does not see that the God in the Old Testament and the God in the New Testament is the same one." I am not arguing that the God of the Old Testament differs from the God of the New Testament. In fact the Bible says they are the same God and you will see later on that I use this connection to then prove Jesus is not the messiah. Where do I start? I suppose I will cite several Bible versus in which I will objectively try to demonstrate God's acts of injustice. To start: Exodus 12:29 And it came to pass, that at midnight the Lord smote all the firstborn in the land of Egypt, from the firstborn of Pharaoh that sat on his throne unto the firstborn of the captive that was in the dungeon; and all the firstborn of cattle. Slaying the first born in every family regardless of their actions. It is a rather odd decision when you think about it. It's a 'one size fits' all slaying that God chooses here. The Bible's justification here is God's desire to force an exodus of the Jews from Egypt. He of course sees murdering thousands of innocent people as the answer. Genesis 6:7 And the Lord said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them. This one is too, odd. If God was omniscient and all knowing, how did he get convinced by a mortal human to change his mind? His justification was his displeasure of human action and decided to exterminate all human beings. But if he was all knowing, wouldn't he have foreseen this in human nature anyway? But Noah convinces God to spare humanity. How does an all knowing God change his mind? Any-who, again God sees it fit to murder countless people. Numbers 11:1 And when the people complained, it displeased the Lord: and the Lord heard it; and his anger was kindled; and the fire of the Lord burnt among them, and consumed them that were in the uttermost parts of the camp. So God committed aggravated murder here. Which struck me as kinda weird considering this is in Go's scripture: Ecclesiastes 7:9 Do not be quickly provoked in your spirit, for anger resides in the lap of fools. Is God a fool!? 2 Kings 19:35 And it came to pass that night, that the angel of the Lord went out, and smote in the camp of the Assyrians an hundred fourscore and five thousand: and when they arose early in the morning, behold, they were all dead corpses. That's 185,000 soldiers! This is a good one. So does this seem just to you? Israelis are waging war with the Assyrians. God again deems it fit to slaughter thousands of soldiers to protect his chosen people. Now you believe that God created all these Assyrians and knew every action they would take because you also believe he is omniscient, yes? So God had pretty much damned these people from the start don't you think? He created them and placed them in Assyria. From then on all these men lived their lives in Assyria until being enlisted into the army against their will. Then while fighting in combat God smites all of them. Now since they're all dead and they were not saved or believers of God, they all now spend eternity in damnation. Justice? I think not. I fail to see the all merciful loving God here. 1 Samuel 6:19 And he smote the men of Bethshemesh, because they had looked into the ark of the Lord, even he smote of the people fifty thousand and threescore and ten men: and the people lamented, because the Lord had smitten many of the people with a great slaughter. 50,000 slaughtered, even the Bible uses slaughtered in this verse. God had the Ark available to these people. Since you believe God is omnipresent and omniscient, then we can safely say god knew that these 50,000 people would be tempted to look at the ark of the Lord, for all eternity. Does it seem like God is tempting these people. Now this is critical to understand, who is the great tempter in the Bible? Satan! and what is God essentially doing here? 2 Kings 2:23 And he went up from thence unto Bethel: and as he was going up by the way, there came forth little children out of the city, and mocked him, and said unto him, Go up, thou bald head; go up, thou bald head. God's victims in murder here are the youth. Why? they made fun of a man's bald head. Kids being kids, now they all have to be murdered. There are also many laws in Leviticus in which if the law is broken, the penalty is death. John 10:30 "I and the Father are one." That is Jesus saying he is the son of the God of the Old Testament. He is the God of the Old testament. The God of the Old testament is unjust, a tempter, merciless, and therefore not real. Jesus is not the messiah. Where is the justice here? answer me that. Feel free to quote me in your rebuttal. All Bible versus are from the King James Bible. Excluding Ecclesiastes 7:9, which is from the New International Version.