It wouldn't need to drop grenades. It could pick you up, fly high enough, and drop you to your death. Never runs out of ammo, just batteries.

This is pretty horrifying. Bonus points if you hit somebody on the way down?

If a drone wanted to kill you, it would use a bullet. Cheapest and easiest way, with the least risk to the drone.

The extraction case would only be for high-value targets (enemy military/economic/political leaders), where having them alive would give leverage on having them order their organizations to do something useful for the drone owner.

Bullets are probably more economical.