(Fate) full power counter guardian heroic spirit?

[Nasis]

For what I understand, counter guardians get power of counter force from earth enough to deal with their target If heroc spirt get full might of counter force, can any heroic spirt can reach tier 5? For example if world choose archer(EMIYA) to deal with moon or planet level enemy, will he be empower to reach this level too?

I wonder how powerful is heroic spirt Gilgamesh with full power of counter force

Tell me if I misunderstand something