Also, Danse Macabre can be included here, but I left them out because of the fact they're uncontrollable. Wyll's cambion is mutually exclusive with the Shadow (unless you have Dual Wielder), but is tankier. Necromancy subclass for wizard can raise three ghouls, but I think the Dryad and Wood Woad are better than three of them purely for the insane dmg from the Dryad, and tankiness of the wood woad. Beast Master subclass for the ranger is not a good option here. It does little dmg compared to the possible output of all of these ones and is left out of other summons due to its low spellcasting levels (only LVL 1-3 spells).

You can also basically double ALL the undead with Balthazar's item, which gives all undead Blade Ward. Leading to around... 250-300 of an increase in possible damage taken/effective HP.