Mega-Potion

Taken all the way down to base materials, a batch of 3 Mega-Potion is 2 crafting steps deep and needs 1 intermediate — Distilled Water ×1 — which resolves to 3 distinct raw materials totalling 3 units, plus 11 crystals.

That bill outweighs 3,373 of the 13,602 recipes tracked here and 426 of the 1,591 Alchemist ones, and 4,464 recipes nest deeper.

Only 10 of those crystals go into the final step; the other 1 are burned by the intermediates, so the real crystal cost is 6 Water Shard and 5 Lightning Shard.

Every step is Alchemist work, from a Lv 1 intermediate up to the Lv 43 finish, so one class covers the whole chain.

All 3 raw materials are gathered, and not one of their spots is timed, so nothing in the tree waits on the Eorzean clock.

Mega-Potion is itself consumed by 1 further recipe, all of them Alchemist recipes.