I like dealing neutral damage to EVERYTHING.
So let's start with Alm - the guy with the best neutral offensive bow spread (37/37). From there. . .
Weapon: Argent Bow (hits twice, can eliminate the speed penalty entirely with a speed refine or go with Chill Def 3)
Special: Growing Wind (wait WHAT)
A skill: Atk/Spd Push 4 (best combat bonuses I can think of)
B skill: Killing Intent (since everything should've been dinged with Growing Wind)
C skill: Human Virtue (boost his own offensive stats) or Solitary Dream (and now he moves three spaces)
S: Brazen Atk/Spd 3 (because at this point everything should wish that it was dead)
Assuming he stays between 25% and 80% of his max HP, you're looking at four attacks backed with 64/56 offensive stats (62/54 with Solitary Dream). And this is before merges, or a +Atk asset.
Chill Def 3 should guarantee kills on everything. Without Chill Def 3, Spring Lukas survives.