Bro, Gilgamesh literally used the same types of weapons just higher in rank in UBW. Arturia literally did not change weapons while killing Berserker in Heavens Feel Archer killed how many lives of Berserker in Fate Route. If Godhand really made him 100% immune killing him once with a sword means he won't ever die again from a sword cut or cut in general. But, it doesn't it just increases his resistance to what killed him. Cleave has no limits, it's a constantly adjusting attack, a pretty bad match up to someone who gains "resistance" it's an attack that literally "cleaves the world" to get past an infinite amount of distance.