User blog comment:IamJakuhoRaikoben/Chapter 496: Forward, Review./@comment-4945830-20160801190726/@comment-1359322-20160802022139

Rather than Job Serena being at 1/3 of his strength, i think what Gildarts is saying is that if Serena was alive, he could at least take a few full power punches from Gildarts but since he's just a Historia now, 1 direct hit and he's gone.