Put the bullet where it's effective and hope. That's all anyone can do.
Emperor in on a rare Sunday visit.
Yep! And do that while under the most stressful situation or mental duress that you will EVER be in as a civilian.
Sooooo, in summary: With the best available ammo (already available on the market), load out (everyday), a tier 1 pistol you can comfortably carry and rapidly and effectively deploy, that can hold as many rounds while maintaining the aforementioned criterion, along with (at least one), spare magazine loaded with the same ammo.
When that moment of truth arrives (I hope it never does FOR ANYONE (more so myself)), and when you consciously decide, shoot as many bullets into the potential threat as you possible can while moving, and hope; as dwr461 suggests, that one or (hopefully), more; strike spine, brain, pelvis, or femur, to render your attacker unable to continue.
If you kill the threat instantly; it's lagniappe!
Shooting a person in self defense is like sales; "Cast a wider net!"