What armored unit uses steady/warding breath the best? (Both base kit AND with any B Fighter)

A +Res/-Hp Hardin would suit a WB set with Bold fighter and QR seal.

Hardin with Warding Breath, BK Steady Breath. Basically any Armor unit with a built in DC will want it.

zelgius with boldfighter is the best use of it, breath skills work well with dc weapons which he has+an op special. combined with ostias or quickened pulse whether the enemy attacks him or he attacks them they have to eat a black luna if he's +atk he becomes an huge threat ;p
hardin with aether is great for a more sustained tank for use in tt and chain challenges

+Def Zelgius is terrifying with Steady breath and QR/VF

Some more builds with Bold fighter:

Effie/Gwendolyn- Gale force/Bonfire ,Firesweep L, Death Blow, Bold Fighter.

Grima- Aether, WB/SB/Brazen Def and Res, Bold Fighter, Qr seal.

Hector- Aether, DC, Bold Fighter Qr seal.

W!Tharja/LA!Lyn- BladeTome, Glimmer, CC, Bold fighter, QR or Close Def Seal.

H!Jakob- Brave Bow, Ignis, CC, Bold Fighter, Close Def or QR seal.