I'm going to assume you mean Multiscale Lugia, although it doesn't affect the answer, which is, believe it or not, yes! The most powerful possible unaffected (by boosts, terrain, abilities, etc. etc) move to hit Lugia with is a Head Smash coming from Mold Breaker Rampardos (which, by the way, is an ABSURDLY powerful attack), and it does this:
252+ Atk Choice Band Mold Breaker Rampardos Head Smash vs. 252 HP / 204+ Def Lugia: 596-704 (143.2 - 169.2%) -- guaranteed OHKO
^with Choice Band
252+ Atk Mold Breaker Rampardos Head Smash vs. 252 HP / 204+ Def Lugia: 398-470 (95.6 - 112.9%) -- 75% chance to OHKO
^without Choice Band
252+ Atk Choice Band Rampardos Head Smash vs. 252 HP / 204+ Def Multiscale Lugia: 298-352 (71.6 - 84.6%) -- guaranteed 2HKO after Leftovers recovery
^with Choice Band, but without Mold Breaker
The only other moves capable of doing such are the OHKO moves (Guillotine, Sheer Cold, Fissure) which aren't legal in competitive play.
Antacool I need you to make a legit Trick Room team for this mon and if you do i will love you forever.
EDIT: I lied, Choice Band Zekrom is able to do it as well, but ONLY Choice Band, and with either Fusion Bolt or Bolt Strike.