Ok, listen close, listen well. I feel like you're asking this question because you want to buy something for self-protection, right?

If someone wants to rob you, you're going to get robbed. If someone wants to stab you, you're going to get stabbed. If someone wants to murder you, you're going to die.

It's almost always going to happen when you do not expect it, when you're not prepared. That's the whole point.

Number 1 rule in these situations: Run. If you have the chance, run. Do not try to fight, just run as fast as you can.

The videos you see on Youtube of people taking down an attacker are just people getting very lucky. The other 99 times, it goes the other way.

That being said, if you think you'll feel safer with a self-defense weapon, go ahead. But keep in mind that you only use it when there's absolutely no other option.