Perfect pokémon means pokémon that can counter all of their weaknesses with super effective attacks. Here's a list of every perfect pokémon I know:
HO-OH
Sacred fire
Sunny day
Solarbeam
Earthquake
Not really recommended, as Ho-oh can learn Recover, which should never be deleted. This one...
HO-OH
Sacred fire/Fire blast
Recover
Giga drain
Earthquake
...is maybe better. Although Giga drain is only half as good as Solarbeam, it makes Ho-oh recover and Sunny day is not needed. Recover will come in handy, though, as sometimes you need to recover more than the bit Giga drain will do.
ENTEI
Flamethrower/Fire blast
Sunny day
Solarbeam
Something
A very good one, as Solarbeam counters all of Fire's weaknesses. The last slot is your choice.
FERALIGATR, BLASTOISE or ANOTHER WATER TYPE that can learn these
Surf
Ice beam
Earthquake
Something
I recommed Blastoise for this, as it has good attack AND special attack.
LANTURN
Surf
Ice beam
Rain dance
Thunder
As Lanturn is a Water/Electric type, it is not weak to Electric, leaving Grass and Ground as its only weaknesses, Ground being easily beaten by Surf and Grass by Ice beam. If they freeze, Rain dance will prevent them from thawing out, as well as making Thunder accurate and Surf more powerful.
PIKACHU or RAICHU
Surf
Rain dance
Thunder
Double team
Attach the Light ball if it's a Pikachu. (The Light ball is the reason why I'm even mentioning Pikachu)
ANY NORMAL TYPE that can learn these
Psychic
A good fighting attack
A good bug attack
A good ice attack
Okay, the idea of this set is that Psychic will take care of Fighting types, but then you're in trouble against Dark, Psychic and Steel. Bug and Fighting beat them all. But against Dragonite, it's good to have an Ice attack ready.
LUGIA
Earthquake
Shadow ball
Rock smash
Ancientpower/Recover
This one is NOT recommended. Rock smash is simply too whimpy to be of any use against Darks. But I had to list it as it counts as a "Perfect" pokémon.
ZAPDOS
Thunderbolt
Thunder wave or something
Steel wing
Drill peck
Zapdos' main strength in weaknesses is that it's the only Elecrtic type that's not weak to Ground. So, it's not weak to Electric, and then only Rock and Ice are left, both beaten by Steel. Drill peck is just for Grass types getting in your way.
ELECTABUZZ
Ice punch
Thunderbolt
Barrier
Rolling kick/Cross chop
Ice punch is to get rid of Ground, while Rolling kick and Cross chop take care of Normal types with Ground attacks and Tyranitars.