Most Helpful Girl
Well, according to the biblical origin of the sins, Pride is the first and deadliest sin. It is the one from which all other sins are born.
This is somewhat supported by the field of psychology, because it's from issues with one's pride (i. e., overinflated/deflated levels of self-esteem, confidence, etc.) from which many other issues (e. g., mental illness, poor social outcomes) can arise.