I think they fixed the solution that worked in the PS3 version in The Handsome Collection. I could not get the Bandit Technical glitch to work. You will have to wait until level 31 to get this - complete the Bloodshed track and the last one - Many Must Fall - will add time for melee killing an enemy. Find an area with low level varkids or skags and wait until you have 5-6 around you. Go into Deception mode and melee everything. It will not take long and make sure you do not have a spike shield equipped.
If you're able to moonshot powerlevel an assassin, you can get this in the beginning of the story with the bullymongs.