Know Your Enemy is a companion perk in Fallout 4.
Obtaining
To gain the perk, the Sole Survivor has to reach maximum affinity with Paladin Danse and complete his personal quest Blind Betrayal.
Siding with the Minutemen or the Railroad before completing Blind Betrayal will lock this perk away.
Effects
The player character deals 20% more damage against ghouls, Super Mutants and synths.