Metal: Hellsinger

After completing the first level, you will have access to Torments from the level select menu. These are smaller challenges, with some kind of extra condition that must be met, such as "Your weapons randomly change after each kill."

To get the top result, you need to achieve the stated goal on that Tormet, such as killing a set number of enemies within the time limit. For me, the "your weapons change randomly" Tormet was the easiest of the first set, since you never need to worry about reloading; you just move from shotgun to sword and back again after each kill. Stay just out of arm's reach of the enemies, move in for the sword kill, step back for the shotgun kill, and repeat until the kills are done.