If you had a Lugia at lvl.100 and the multiscale ability, and IVs in every stat, and had an EV spread and nature where needed (so if it took a physical hit then imagine it had 252 HP / 252 Defense, with a defense boosting nature; and if it took a special hit then imagine it had 252 HP / 252 SP. Defense with a SP. defense boosting nature), would it ever die from one hit, at 100% health, from any Pokemon and any attack?
EDIT: Discluding any OHKO moves such as fissure. Sorry, but I already knew about those ones.
Please also put calculations in the answers, thank you!