What Nietzsche is right about
Selflessness is a bad ideal. (He explains it as cruelty turned inward.)
Morality motivated by resentment is bad.
Rejecting life and longing for nothingness is bad.
If Christianity holds selflessness as the moral ideal, motivated by resentment of the powerful, and rejecting the only life and world as one has known it in the unrealistic hope for an afterworld that is better; then it should be rejected.
It is good, not bad, to want to have more power over one’s own life.
Antisemitism is stupid and boring and born of the resentment of a feeling of inferiority.
What he is wrong about
The will to power is the only real motivation in all living things, including humans. Master morality celebrates the will to power and directs outward the cruelty that it necessarily involves. Slave morality condemns the will to power as immoral, even though it is just as motivated by the will to power as master morality is. It directs inward the cruelty required by the will to power and hence promotes the false ideal of selflessness.
Christianity holds selflessness as the moral ideal, motivated by resentment of the powerful, and rejecting the only life and world as one has known it in the unrealistic hope for an afterworld that is better. Hence, Christianity should be rejected.
God is dead, and we have killed him.
The goal is to overcome oneself as one now is and to become Superman, like the god Dionysus.
Pity is bad.
There is only one world, and we each have only one life, although this same world and life in every detail recurs eternally.
Considerations in support of the claim that he is wrong about those things
From a subjective point of view, there is no discernible difference between living your life only once and never again and living your life over and over again eternally in exactly the same way each time.
If God is dead, that means that what you previously thought to be of ultimate value you no longer believe to be so. But as long as you believe there is something of ultimate value, you believe in God, whether you use that word or not. Thus, to be an atheist is to deny that there is anything of ultimate value. But that is contrary to experience.
Jesus said that the supreme commandment is to love the Lord your God with all your heart and all your mind and all your strength and that a second command that is like it is to love your neighbor as yourself. This implies that you should love yourself, because if you don’t love yourself, then loving your neighbor as you love yourself would mean not loving your neighbor. It also implies that loving God with all your heart and all your mind and all your strength and loving yourself are like each other.
Loving God also means loving your life as it has been given to you, with all its limitations on your ability to control things, such as unavoidable suffering, grief, and loss. Thus, your having power over those things is not what is of ultimate value, and the will to power is not the ultimate motivation for everything you do.
There is no good line of reasoning, either deductive or inductive, to believe that you will ever be permanently unconscious, even though there are plenty of good reasons to believe you will die at the end of this life. You have never been permanently unconscious, since you are conscious now, so first-person experience could never show that permanent unconsciousness is a likely outcome; and the nightly and daily transitions from being awake to dreaming and from dreaming to waking up constitute a strong inductive base for the conclusion that the transition from being alive to being dead is probably experienced subjectively as something similar. Therefore, you have good reason to believe you will have other lives besides this one in other worlds besides this one, even though the life you live will always just be your life, and whatever world you find yourself in will always be the one you call “this world.” Alternatively, we may say that this world consists of many worlds and your life consists of many lives. Either way, it is perfectly rational to hope that sufferings you have to endure will be compensated by future as well as past joys, even when the suffering takes the form of sickness leading to death.
There is nothing condescending about true pity, which recognizes in the suffering of someone else the same thing as one’s own suffering. We should all feel pity for each other because we all suffer and die and see loved ones suffer and die. But we should also feel a brotherhood and sisterhood of joy, because it is a good and joyful thing to be alive, and none of us is going to die utterly into nothingness ever.