Sometimes I really should stay away from the comments…

Self-defense classes, a gun (with training), being aware of your surroundings. If possible, don’t comply with leaving a location with over 90% chance you’ll be murdered and they’ll have privacy to do it.

A knife was mentioned - you’re more likely to be injured or have it turned on you so not a good weapon. A taser - if you can maintain some distance this might be good; depends on which one you have. Pepper spray - expires, also can come back on you and may not disable an attacker.

And pointing out the most important thing, you’re more likely to be harmed or killed by someone you know rather than the stranger in the alley.