What makes Gilgamesh so strong is the number of Noble Phantasms he has.
'Uh I didn't have any proof, but I thought that I might have the best luck against him.' 'Huh? You said you're going to fight him when you haven't realized that?' Oh, so you realized it too, huh? Gilgamesh's natural enemy is Archer's magic.' Part 223: Rin's proposal (lethal dose) / Mind and body Music: Tender Scenery