(This was made in update: 25.1.1 so uhh this might get outdated)
Ok so Nekros is a supportish class which can also draw aggro with shadows, and cc with terrify, and support with Desecrate
So first ablity Soul Punch
Fun fact: IT SUCKS. It's definetily Nekros' worst ablity. Only use this when you are either leveling or just have this stupid max strength build. In that case, why in the world would you do that?! Lets just skip this one.
Next, Terrify. Use this when doing stuff like reviving a teammate or there is to much people harassing the cryopod or something. This can also reduce armor, and with the augment can slow so it's pretty useful. This can stop any enemy from harassing an objective, and make them easier to deal with. So yeah not much to talk about here except the fact that this thing is good
Nekros' 3rd ability is Descrate, which is probably what you picked up for here, lets be real (unless you were like me and didn't even study crap before chosing someone to main). It make dead people reroll drop chances, so use this when farming and supporting. Oh and another thing, if you have the augment, Despoil, Equlibrem and Health Conversion are your best friends. You will be getting a LOT of health orbs from enemies more so than energy orbs in my taste so you will also be getting constant energy and and with a maxed health conversion you will be getting a constant whopping 1415 armor, and this will be consistant. So yeah, GET THIS FREAKING AUGMENT.
Shadows of the dead is Nekros' last ablity This is another cc ability which draws in aggro and deals and decent amount of damage. These Shadow go off your strongest killed enemies in the last 20 kills (For more info check the actual Nekros page). This is good for distracting enemies but beware that if you want them to do dps, keep in mind mind controled enemies kinda suck. Also with the augment and the previous said constant 1415 armor, you can have a Nekros be a bullet sponge with 98.25% damage reduction. That is HUGE.
So builds. Ummm screw strength. Unless you want a maxed out terrify build then don't use strength. You mainly prioritize duration and range, with efficiency being just a cherry on the top. Also keep in mind that Nekros and its prime does not have a aura polarity. You might want to forma it with a normal forma or an aura one.
Hope this guide helps, this is my first guide and feel free to complain or ask me questions!
P.S Sorry for the lack of pictures