From a theological standpoint, Jehovah fixed his own mistake by manifesting as Jesus. The Father and the Holy Ghost, two non-physical aspects of God, tried to watch over a sinful world and we have the destruction of Sodom and Gomorrah, the Great Flood, etc. proving that no matter how much God tried to fix Evil, mankind just kept coming back worse than before.

So the solution was to endure the pain of the entire world, to pay for every sin that mankind has ever made and will ever make. Meaning and intent is everything, and it's kind of hard to make all of that pain and sacrifice meaningful if you're a nonphysical representation of Eternity and Infinity. So God had to manifest Himself as a single, physical, finite entity that is separate yet part of a whole.

And so Jesus comes into the picture. In Christian Theology, Jesus is the ultimate manifestation of God: The enlightened, holy man who becomes one with God and His infinite wonder. Whether you believe Jesus was God since his birth, became God through his actions and wisdom, or didn't even exist at all except as a legend, the fact is, Jesus became a symbol for ultimate, innocent purity. He was the man who could not sin. He was the man who did not deserve pain or suffering of any kind.

And that is why he was the perfect candidate for the ultimate sacrifice. A being so pure selflessly gave the one thing he deserved away, and he endured all the pain and suffering of the world so that no one else would have to pay for something inherently part of their nature.

So by dying, he achieved apotheosis and ascended to the heavens to become one with God, and he is supposedly coming back to finish off Satan once and for all, and mankind will live happily ever after.

So in order to be absolved of your sins, there are various denominations that tell you what you have to do. In general, Protestantism says that you need only believe in the sacrifice Jesus made, and you will enter heaven. Catholicism, on the other hand, teaches you that not only do you need to believe in Jesus, you also need to respect/worship/honor the Saints, and that you are also still accountable for your sins, but they need only be washed away in Purgatory before you enter Heaven instead of burning forever in Hell. There are many other views, but faith in Jesus is pretty much the only thing that is similar.