Did you read what he said? 1 Nasty Plot and Life Orb Beam kills 252/252 Blissey. No Crit Needed.
Oh god can you please do some damage calculations.
405 attack vs 306 defense, 150 power(*2 *2), 714 max HP: 79.97% - 94.12%
Does not OHKO. Blissey switches into Nasty Plot, takes a Hyper Beam and Calm Minds. Already Blissey is at 459.
You will recharge as Blissey Softboileds.
Also, in your initial post, you fail to mention Life Orb, in which case, you would still not OHKO if I just say I maxed Special Defense.
405 attack vs 405 defense, 150 power(*2 *2 *1.3), 714 max HP: 79.13% - 93.14%
At which case if you Hyper Beam again, it still won't kill.
405 attack vs 459 defense, 150 power(*2 *2), 714 max HP: 53.78% - 63.31%
Blissey will Calm Mind again regardless if you Nasty Plot or Hyper Beam again.
405 attack vs 612 defense, 150 power(*2 *3), 714 max HP: 60.64% - 71.43%
That is after 2 Nasty Plots and Hyper Beam. If you Nasty Plotted the second time, Blissey would have had Calm Mind again. Therefore that's hwo much you would have done with Hyper Beam. Of cuorse Leftovers would prevent yuo from killing.
Also, this is all assuming that I'm using minimum special defense Blissey, so therefore please don't talk shit if you don't even have the facts. Thank you.