Flawless victory
From Guild Wars Wiki
A flawless victory occurs in PvP when a team successfully prevails against the opposing team or teams without any team member deaths.
In other words, if a team wins without any team member dying, then it is considered a flawless victory.
In 4-man level 20 arena's (Random Arenas and Team Arenas) a flawless victory grants you an additional 100 faction with Balthazar, the god of war.
