Does fiddlesticks counter swain?

Fiddlesticks counters everyone. Whoever he Q's is effectively countered. He gets to choose who, but it's up to his team to follow up on it.

Also, get morello~ to counter his W. (goes both ways tbh since you both have strong heal abilities). You get countered more so than him though. He doesn't rely on heal to do well, as it's easily canceled anyways. You do rely on your heals though.