In this Destiny 2 video by Aztecross Gaming a One-Hit Melee Build is created.  It's for Titan players, and sees Artifact mods act like temporary buffs that change the way we play the game. 

The Artifact that is used in this build is Thunder Coil.  The icon looks like a fist with lightning bolts coming out of it. 

The damage increase in PvE is approximately 50% to melee damage.  Aztecross Gaming put the following together for 105,903 damange punches

• Biotic Enhancement + Thunder Coil + Knockout + One-Two Punch
• He also tried Peregrine Strike + One-Two Punch + Seismic Strike + Thunder Coil for 323,591 damage!

But!  

• Peregrine Strike + One-Two Punch + Hammer Strike does 400,007 damage!

In PvP once you proc Knockout you can one punch kill any Guardian. Watch the video for a full explanation: it's time to go to Pound Town!