Annan's strength was three times that of an ordinary dragon, which was precisely why he could so easily defeat the replicated Nicholas.
Neither of them had high physical strength attributes when in human form.
Even if Annan could stack his will attribute on top of his strength attribute, it would likely be a drop in the bucket compared to the natural strength of a dragon.
However, this tripled power allowed Annan to catch the Demon Dragon Nicholas off guard and immediately restrain him, leaving no chance for escape.
—Until he used the Element of Victory to adjust his strength to be even stronger than Annan's.
But Annan would not give him the chance to break free.
The sealed form of "The Third Siren" had besides the "triple experience" and "triple damage," actually had an active effect: