Here is the full list of all 35 Nekro achievements.
Find and befriend the Giant Flaming Bear.
Kill 35 Priests.
Beat the campaign without taking any Nekro upgrades...you dirty boy.
Use 10 different trinkets in one campaign.
Beat the campaign with the Outcast Powerset.
Beat the campaign without eating any animals.
Pull 50 enemies with the Outcast's chain.
Beat the campaign with the Grimm Keeper Powerset.
Kill 35 Zealots.
Summon 30 Darkseeds.
Smack 50 enemies with the Grimm Keeper's skull bag.
Beat the campaign without dying.
Beat the campain with the Alchemist Powerset.
Beat the campaign without using any Trinkets.
Issue 500 orders to your summons.
Kill 50 basic Townies.
Kill 35 Hunters.
Defeat the Citadel stage without dying.
Kill 35 Witches.
Throw 50 healing vials.
Kill 35 Townie Elites.
Summon 30 Punges.
Deploy 100 scourge.
Issue 250 orders to your summons.
Issue 150 orders to your summons.
Issue 50 orders to your summons.
Issue 10 orders to your summons.
Summon 30 Horrors.
Defeat Mayor Biscuit without dying.
Kill 30 chickens.
Kill 50 Lumbros.
Kill 10 Mushroomheads.
Kill 30 Pigs.
Do any description of anything.
Bestow the moniker of "Vance."