ADVENT Stun Lancer (XCOM2)

A specialist ADVENT soldier wielding an electrically-charged baton/sword and a magnetic rifle. Their greatest threat is their fearlessness in performing dashing attacks with this blade: if it gets within range, expect it to rush you within the next turn, even foregoing cover and gun to attack a soldier. Despite their name, their melee attacks are most definitely lethal, and in addition can inflict disorientation or stun as an extra effect if the target survives. Flashbangs are helpful in restricting their movement, since a Stun Lancer who can't reach you is only as much of a threat as a regular Trooper. Setting an overwatch ambush for them can also be effective. Remember they also have rifles, so don't just back away ignoring cover like you might against other melee enemies.

Blademaster Ranger with an upgraded blade has a chance to inflict burning or disorientation on this guy, disabling his melee attack. While generally beneficial, this will give him free move and free shot, most definitely a close range flanking one.