@Muhammad Abdul Aziz Habibi Why would a servant care if you defeated them? Servants are absolutely NOT loyal to the same people across summons, they don't give 2 craps who's summoned them and who's defeated them before except in very special circumstances such as Serenity remembering the master who cared about her.
They're contracted as mercenaries, tools, to fight for your side. Although they still have their own will, only certain types of people are summoned, ones that believe in working as a tool to help advance the ideals of the living human that summoned them. That's their contract. And once that war is up, once they're unsummoned, they honestly couldn't care less who won or lost.
You're not their "enemy" just for defeating them, you're someone who was in a holy grail war with them. Only living people or beings will ever care about being defeated, which only refers to the Lostbelt masters (and the demon god pillars back from chapter 1), who are normally KILLED by the end of the lostbelt. They can't be summoned as servants, their grudges died with their corpse. Yu Mei Ren lives with us because we summoned her husbando Xiang Yu.