Options for the Hunter Ranger Archetype
Hunter's Prey (3rd level)
Night Stalker. You are a living weapon against creatures that stalk the night. Your weapon attacks count as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage against shapechangers and undead.
Defensive Tactic (7th level)
Blessed Fortitude. You have advantage on Constitution saves against disease and effects from undead.
Superior Hunter's Defense (15th level)
Chosen. You have no need to fear the rot of undeath. You have immunity to necrotic damage.