Desperado used to be a Pinnacle Weapon unique perk on Redrix's Broadsword. But has now been added to Trials loot pool via The Messenger. And this is the version that wasn't nerfed, still doing full damage per shot while boosting the fire rate to insane levels and bringing it's TTK in PVP to .5 seconds. This seams to run counter to Bungie no longer introducing Pinnacle weapons with their unique perks and creating Ritual weapons instead which only use existing weapon perks. There seem to be only two reasons to add these powerful perks back to the loot pool. Either they're adding them to Trials in an attempt to boost player number in this activity to justify the expense in creating new weapons and armour for this niche mode. Or they're bringing more of these old perks back to other loot pools in the near future to vary weapon drops more.