As I see it, any competent servant can defeat her. Even though she has the offensive powers in the form of her shadows, they have been defeated by rin who was using sword of zelretch. Now the sword was OP but it's more about the speed of the shadows, a human countered them before they could harm her. Past that, sakura herself has the stats of an average human and regeneration to some extent which I see any strongest melee servant getting through as they move with hypersonic speed which she would have difficulty even perceiving. And that is considering while they aren't handicapped in any way or didn't fought indirectly.
In gilgamesh's case, he needs to spam some ea and that would do the job. Only reason he was defeated was because he wasn't paying attention. Though I did like the fodder treatment.
I'm yet to play/watch heaven feels(the movie ain't even out yet) but form what I heard, she pretty much wrecks everyone in that route, but hey ea can "erase all of creation" so there you go.:lol
Ea was rendered useless against Avalon in Fate route.
