The Scorned Sword Bounty in Destiny 2 is a new daily bounty that you get from a Seraph Bunker. You can complete it in two ways. The first is the kill a Guardian with a Sword, which can be done by heading for the Crucible playlists, bringing a sword, camping the heavy ammo spawner, then murdering someone.
If you would prefer to take out the Scorn Boss, then you can head for the Dreaming City. Spawn in at the Divalian Mists, then turn around and head for the Lost Sector behind you.
This area is called the Bay of Drowned Wishes and is filled with Scorn and a multitude of Screebs. Fight your way to the end and you will find a Scorn Boss who will count towards this Bounty. Kill them, and the Bounty will be complete.
It’s not a particularly tough area for veterans, but newer players might struggle a little bit. As long as you don’t run too far ahead, you should be able to handle all the Screebs that spawn in and make sure to take out the bigger enemies, as the first few Screeb groups will respawn while those monsters are lumbering towards you.
Be careful when you reach the energy wall, as you need to kill everything else before it will drop, allowing you to proceed. Jump on top of the nearby rocks so that the Screebs cannot get you, then pick them off as they spawn in. Killing one early enough after they spawn will take out the entire group, making life much easier.
For people who don’t have the Dreaming City opened yet, you can always head for Kingship Dock on the Tangled Shore. This Lost Sector will house another Scorn Boss for you to kill.