Frisk's insane agility, mastery in Martial Arts and Knife/Dagger usage, recallable BS techniques, and "Sukuara" form gave him the upper hand in this battle. Mercy's superior precision and tactical skills were not enough to beat Frisk's overwhelming power and ability to use the environment to its full potential. In a dire situation, Frisk's ability to switch to Chara ensured a guaranteed victory. Moreover, Frisk's Domain Expansion technique became the deciding factor in this battle as it engulfed the whole area in slashes and resisted death, making it almost impossible for Mercy to escape.