Pistols, bullets, all magnum everything!
Magnum cartridges come in several sizes. Why do we need magnum cartridges? How hard do we really need to hit? The answer is simple. When you have to knock your target over with one bullet.
The 44 Mag, 50 AE, and 500 Magnum are the typical cartridges of choice. The 500 Magnum is clearly the winner of the bunch but only because the ballistics are massively overwhelming.
Mass versus speed is the fastest way to quickly increase the ballistics quality of the projectile. More mass equals way more force when penetrating the target. More gun powder means way more pressure which leads to pushing the heavier bullets way faster.
The Desert Eagle is my favorite for semi auto loading speed and being able to deliver massive speed to the target. While I don't recommend this for everyday training you can't help but have some real fun with these hard hitting rounds. Stay safe, be smart.