God, otherwise unknowable and ineffable, descended to our level and took on human form. He experienced things as we do and lived the blameless life that none of us could, though being tempted daily just like a normal human is tempted. He both served as a perfect moral example for mankind and offered himself to be destroyed in order to appease God's wrath against humans.
People who aren't lacking in self-awareness understand that, over the course of living, to some extent or another, we either think or actively do things that are inexcusable and objectively depraved. Some people, lacking in self-awareness, deny that they've personally done such things, but this is untrue. All human moral codes have assumed that, for the greater good, wrongdoers must be punished. If we are to apply these standards consistently, we too deserve to be punished. And under God's moral code, which is the most perfect and consistent moral code, and which he has the power to enforce absolutely, we deserve to be punished more harshly than our own codes would allow for, since we don't dare assign ourselves a punishment weighty enough to match all our crimes. This is the source of God's wrath.
God dealt himself a punishment weighty enough to match all our crimes, which were the consequences meted out for our crimes, hence we don't have to be punished for such. This may seem irrational, since God could've just not punished anyone including himself. Were this the case, however, then it would create an amoral reality where evil is not punished and good is not rewarded. To uphold a moral reality it was necessary for someone to be punished.
God expects that humans who are recipients of mercy desist from further violations of God's moral code. Perfect compliance with this expectation is impossible. One of the great unsolved questions of Christianity is what degree of non-compliance will be tolerated without said mercy being taken away. There is no consensus on this point, though it's widely recognized that people at least ought to strive to sin less and less over time.
One must also accept the idea of God who assumed humanity, one must worship God as framed by this idea and described in the historical text known as the Bible, and one must ask God so framed for mercy. It's accepted by most that trying to live a less sinful life is futile if you don't recognize God so framed and ask him for mercy, since this is the only way to be a recipient of said undeserved mercy. Without said mercy, you cannot be good enough to merit being spared God's wrath. Hence, other religions are futile even if they promote good works.
