A slot for a normal Marth

Res +2?

Fury is generally a good skill for him to make him really hard to one-round (especially if you're using a support build). Otherwise, death blow and swift sparrow are strong options for sticking it to dragons. He can look for OHKOs against flying Tiki, some versions of Y.Tiki, and all green manaketes; he also needs a bit of extra attack to get through Hector's tough def and HP. You might also find OHKO against some builds of Raven.

Fury's the best all round option.
Brazen Atk/Def would be a good option if he gets access to Exalted Falchion since it has no health regen and you can stack a good amount of buffs.