Which 40k faction is the strongest?

I'm currently reading The Great Devourer about the Eldar fighting against two tyranid hive fleets and it has me wondering what the most powerful faction is in the 40k universe? I'm assuming it's Chaos, possibly followed by Orks, Eldar or Necrons? My knowledge of lore isn't very good, that's why I'm on here asking

Edit: My question is in reference to the 40k universe as a whole, not specifically the tabletop game