Electrohammer Vanguards are Fatui Skirmishers that can inflict heavy amounts of damage with their attacks. They can perform a 3-swing combo attack, starting with an upper hammer swing, then a slam attack, and then a side swing. They can also perform a charging attack, ending with a powerful slam that deals damage over a wide area. One way to dodge this is to just slightly dodge and walk past them to go behind them as they are about to swing their hammer at you.
In combat, the Electrohammer Vanguard can generate Electro elemental armor, granting him heavy amounts of damage reduction and dealing AoE Electro DMG in all of their attacks.
Cryo elemental attacks are the most effective against their shields. When the armor is broken, the Vanguard is stunned briefly, leaving an opening to attack.