Metal: Hellsinger (Xbox One)

Torments are self contained arena challenges unlocked after beating a Hell for the first time, where you have to get a certain amount of kills in the alloted time, and each kill grants you some more time. Each challenge has it's own gimmick to work around (like being unable to heal but dealing increased damage at lower health, or needing to get a kill with a certain mechanic, or kill a certain enemy).

The first Hell, Voke, has the easiest Torments to complete, as it's the first level. The two easiest are needing to get at least 10 on beat kills, or at least 5 kills with your weapon switching after every kill.