Best Special for Slaying/Killer Weapons

I like using Luna with these weapons for sweepers, and Bonfire/Iceberg for high defensive/resistant units.

Best special hinges entirely on the character in question. So the usual rule of 15(50atk/30def/30res) tends to apply. Besides that, some interesting combinations arise based on role, like Steady Breath+3 turn CD specials, or Moonbow+Quickened Pulse, etc.

In a general matter, if you are using a Slaying weapon alone, without any other accelerating special ability, then it's more effective to use the lowest CD special, so Moonbow, in order to trigger it 1 action out of 2, so possibly on every attack.

But in some specific cases where Moonbow's bonus damage isn't patching for the low kill potential of a unit, like a unit with a very low Atk, and if this unit possess a very specialized defensive stat, so a high Def or a high Res, then a 3 turn CD Special that utilizes that stat becomes the optimal option.

For instance, Caeda's optimal build will utilize Slaying Edge and Iceberg together, in order to score a fair number of KO while utilizing her high Spd and high Res.

Here is my build for Caeda :

https://fireemblem.gamepress.gg/q-a/theorycrafting-bravart-caeda-s-tier