START BID 1M 
INSTA 1,6M 
DURATION 2 DAYS AFTER START   
Skill: Serene Grace 
Nature: Bold 
Item: Leftlovers 
Evs: 144 HP / 252 DEF / 108 SPATK 
Moveset: Softboiled 
                 Toxic / Aromatherapy 
                 Flamethrower 
                 Thunderbolt / Thunder   
         This training really surprises, but I used it for a long time, always having excellent results, because opponents never think of facing a blissey of these, with a little training in spatk, Blissey reaches a medium power, capable of giving a considerable damage to certain pokémons , as well as giving 1HKO in Scizor and Gyarados, usually predators of our little friend. 
     Softboiled as stated above, indispensable, to make it last in the battle, toxic and aromatherapy should be chosen according to the need of support of the other team members. Flamethrower, promises to end Scizor, Magnezone, Forretress, Ferrothorn and other steels, while thunderbolt / thunder gives security to Gyarados, Floatzel and other waters that may threaten them. Here comes his skill: Serene Grace that increases the chance of the side effect of the blows working, so it is not difficult to after a flamethrower or thunder the opponent gets burned or paralyzed respectively.   
Other Options 
         There are those who also prefer a Blissey calm, focusing on hp and espdef, in this case nothing that can hit it with special attacks will cause a great damage, however any physical hit can give 1HKO, so in my opinion, I do not know if it can be viable, remembering once again: the strategy is yours !!!   
Counters and team partners 
      Blissey fears stabbed physical attacks, especially Heracross, Infernape, Machamp, able to defeat her with a single hit, as well as the special side Blissey can be knocked down with 3HKO from Kingdra + Rain, or Ninetales + Sun, but I do not think anyone will leave this happens without first giving a softboiled. Blissey fits perfectly in almost every possible time, so there are plenty of options to use beside you, pay for a heavier physical wall to cover it, so you have a physical and special safety on your team. 
             Remember: A well-distributed team is already halfway gone! 
(reference probattlers)