One day, you're going to die. Unless you are fortunate enough to die suddenly, you're going to experience the terror and the pain the comes along with dying. Anyone who cares about you is going to be saddened by your passing.
None of that would be true if you had never been born. Your parents, every parent, has condemned their children to death and has ensured sadness for anyone who comes to care about them.
The worst thing my parents did? Not using protection or having an abortion. Conceiving a child is the most selfish act any person can do.