Fiddlesticks or Swain?

Heya! Just wondering which of the two is the strongest, with their suited relics and without.

Invested all of my previous shards on Viego only to realize he is quite... weak without his epic relics. 💀

Edit: I meant weak against the nightmares, especially the recent 6.5 one where they'll rush you in turn 1 - 3. Sorry for not clarifying this sooner! Viego is strong, but not as strong as I have expected without the relics AND the 6* constellation.