What Class or Class combination will raise the largest controlled undead (skeletal) army in 48 hours?


I am planning on making a Necromancer type with the largest undead army available in 5e D&D. He has 48 hours to build it. I have an existing strategy but would like to hear your ideas.

Rules:

  • Hardcover books only, no 3rd party or UA.

  • You cannot polymorph into a Beholder… (It breaks the story) You have to be a standard race caster.

  • No outside help. You are solo.

  • No prep beyond the 48 hours you have to create the army.

  • Assume you are at a graveyard with access to enough bodies.

  • Lv 20 character, no epic boons unless you have a way to get them through a feat.

  • Prefer no magic items, however if you have one that really makes a huge difference let us know.

  • We are looking to specifically raise Skeletons. No generals required unless it increases the overall army size.

  • All spell slots are available to go towards the army.

  • Buffing the army is not necessary, but if you have a way to do it without diminishing its size, I’d love to hear it.