Malak (prime) might be strong and capable enough to handle Vivicar in a strictly conventional confrontation. However, issue in this case is whether Malak can somehow handle Vivicar's plaque or not. If not, then Vivicar will win.
Bersen'thor defeated Vivicar not just on the basis of raw power but she had acquired a defensive technique to counter Vivicar's plaque earlier. Without this defensive technique, even Bersen'thor may not have stood a chance.