It does, but honestly it is comparable to really any other <insert pokemon with high BST, high BP stab> stacking up tera + condition.Well aside from Fairy and Ice resistance, and you also have absolutely absurd damage output on Flare Blitz under the Sun
252 Atk Orichalcum Pulse Koraidon Flare Blitz vs. 248 HP / 252+ Def Mew in Sun: 283-334 (70.2 - 82.8%) -- guaranteed 2HKO
+1 252+ Atk Zacian-Crowned Behemoth Blade vs. 248 HP / 252+ Def Mew: 237-280 (58.8 - 69.4%) -- guaranteed 2HKO
Yeah Koraidon is naturally stronger than Zacian pre-nerf. Notably stronger too. It is only on Tera Fire STAB and while Sun is up, but wow.
You can do comparable stuff with Kyogre's water spout or Dracovish Fishous Rend or whatever.
It doesn't matter if you hit Blissey for 800% or 101%, it's still dead in 1 hit