Exalted Disgrace?

Assuming you want to keep his legendary weapon, there isn't much to change except the special. Since you have Death Blow 3 and Swordbreaker 3, he would mainly be initiating on sword units that will pose a threat to your team. With his lower than average speed, they're the only units he would always double. I think Dragon Fang is a bit too long of a charged special and would likely be overkill. Draconic Aura is much better and you can get to it faster thanks to the heavy blade sacred seal. His C skill could be better if you're leaning to making him a more offensive type, maybe Threaten Def 3 since he's quite bulky he could take the hit from the enemy that gets in range then debuff them on your turn and KO them with their lowered defenses. But for a supportive skill, I personally find Hone skills more effective since you don't have to stick to a unit all the time to make use of the buff.