I've always liked the idea of necromancy yet compared to other wizard sub classes it can seem weak, such as comparing it to a Enchanter. Does anyone have any ideas for a powerful wizard necromancer (can include sub-classing)

Why do you think the necromancer sub class is weak?

Also nothing is stopping you from picking whatever class you want and casting lots of necro spells.

Weak? No. At level 6 you get an amazing buff to animate dead, and at level 14 you can control extremely powerful undead, even a lich if its used up its legendary resistance uses. 

How is the necromancer weak? All of its features are good, not super situational. If we're comparing it to the enchanter, I would actually think the necromancer is stronger. And, a level 6, your animate dead is epic. Just epic. It's powerful and can you name a wizard subclass feature that's cooler than that?

Necromancer is a STRONG class.  It's major issue is mechanical - walking around with a bunch of Undead following you.    That and arming/armoring them.

Everyone loves False Life.    Bestow Curse while OK at 3rd level, really rocks at 5th.

I particularly like the high level spells.   6th level is freaking awesome - Eyebite, Magic Jar and Soul Cage!

Also remember that School of Necromancy can cast other spells too, so you can still fireball your enemies into oblivion!

Oh i forgot to mention for a low level such as lv 5-6.

Remember that recasting animate dead extends your control by 24 hours on your minions, not just resetting it. So if you know you will need to burn through most of your spells the next day, just recast it before you rest in the evening to have your 3rd level spells available the next day for anything, and potentially another spell preparation slot as well. 

Also, learning dragons breath is a good low level option for improved damage. Hopefully what you fight isn't completely immune to poison, so animate 2 zombies and command them to grapple and trip a guy. Then a third has dragons breath on it for poison damage, and you have it walk up and let loose. The 4th potential undead in my opinion should be a skeleton for ranged options, but another zombie to help the others makes sense as well. You stand in the back throwing the occasional cantrip, but mostly maintaining concentration. Does anyone know if dragons breath would trigger your grim harvest ability?

It should, as long as it does the lethal damage.

It’s not weak in fact at level six with 3 pearls of power (which are surprisingly cheap) and a bag of holding you can have 24  skeletons each Han be given a great sword meaning 48d6 damage a turn with u casting a second level magic missile you can deal a max of 306 damage 

It is one of the weaker subclasses, but its still a wizard so its one of the most powerful things in the game.

It’s not weaker at all. But it really starts shining by level 6. Grim Reaper is horrible, but Undead Thralls is awesome.

I’m playing a Necromancer right now. It’s kind of funny, because this character is a strong pacifist, refusing to kill any living creature, but he didn’t have trouble to animate undeads or actually command his army to do the dirty job.

I have a consistent army of skeletons well equipped with +1 Longbows and my usual tactic is to severely debilitate my enemies with a classic debuff spell like Web, Levitate or Slow, and then follow-up with a rain of arrows from my skellies.

Another common tactic is to distribute grapple attempts with some zombies and then cast Stinking Cloud.

Recently, after reaching level 7, I realized Undead Thralls applies to Summon Undead spell and I’m casting the Ghostly spirit very often. AC 15, HP 47 and 1d8 + 10 attack that always impose a frighten attempt. It’s superior to all other Summon spell options.

Necromancers are really versatile.