I answered how sin and death came and spread among humanity. You don't want to agree with it, so be it. I certainly don't agree with you that God created Adam a sinner, or sinful, because I've found nowhere in scripture that God created Adam a sinner, or sinful.
It was when God told Adam to not eat from the forbidden tree, and Adam disobeyed, and ate from the tree God said not to eat from, that sin and death came into the world of mankind.
It's obvious that God created Adam with the ability to obey him. If it was impossible for Adam to obey God, when God told Adam not to eat from the forbidden tree, then God would not have told him not to eat from the tree, if it we're impossible for him to obey. God didn't, and wouldn't tell Adam to be obedient to something that was impossible for him to obey. So God created Adam with the ability to be obedient to the true God.
Being created a sinner, or being created sinful, would mean Adam would have been created immoral, and wicked, and as I said, God would not have said a sinner or someone who was sinful was very good.