First, rain dance is pretty pointless because thunder in rain after one calm mind is weaker than thunderbolt after two calm minds. This is the moveset I would suggest.
Raikou @ lum berry
Ability: pressure
EVs: 4 Def / 252 SpA / 252 Spe
preferably timid nature
- calm mind
- thunderbolt
- ice hidden power (crunch if your hidden power type isn't ice)
- roar
If your Raikou has 4 Def/252 SpA/252 Spe, its nature doesn't affect its defenses, and it's level 50, it comes out to have 165 HP, 96 physical defense, and 120 special defense. Let's say something at level 50 with 100 base physical attack and 252 physical attack EVs hits Raikou with a base power 80 STAB physical attack, because that's pretty close to what will really happen. Its physical attack stat will be 152. If there are no other modifiers, this is the formula for damage.
(((2*level/5+2)*base power*attack stat)/(50*defense stat)+2)*random*3/2
source
Random is a random number ranging from 17/20 to 1. If you substitute numbers in, you get these two expressions, and the damage will be somewhere between the two.
(((2*50/5+2)*80*152)/(50*96)+2)*(17/20)*3/2
(((2*50/5+2)*80*152)/(50*96)+2)*3/2
According to Google calculator, you'll take between 73 and 86 damage. That means there's about a 3/4 chance you'll faint in three hits and a 1/4 chance you'll faint in two hits. Do whatever you want with that information. My advice would be to set up multiple times when facing a special attacker (because calm mind boosts special defense), once when facing a physical attacker, and don't set up at all if the opponent knows earthquake.
