The Destiny 2 Despised Sword Bounty is a new daily bounty you get from a Seraph Bunker. You can complete it in two ways. The first is killing a Guardian with a sword, which can be done by heading to the Crucible playlists, bringing a sword, camping the heavy ammo generator, and then killing someone.
If you'd rather take out the dismissive boss, you can head to the City of Dreams. Appear in the Divalian mists, then turn around and head to the Lost Sector behind you.
This area is called the Bay of Drowned Wishes and is filled with contempt and a multitude of screebs. Fight your way to the end and you'll find a dismissive boss who will count toward this bounty. Kill them and the bounty will be full.
It's not a particularly difficult area for veterans, but new players might struggle a bit. As long as you don't run too far you should be able to deal with any Screebs that appear and make sure to take out the bigger enemies as the first Screeb groups will respawn as these monsters rush towards you.
Be careful when you reach the energy wall, as you have to kill everything else before it falls, allowing you to continue. Jump over nearby rocks so the Screebs can't grab you, then pick them up as they appear. Killing one soon enough after they appear will take out the entire party, making your life easier.
This is definitely the fastest way in the game to complete the Despised Sword Bounty for Rasputin.