Swords Dance - Doubles ATK -
Nasty Plot - Doubble Sp ATK -
Amnesia - Doubles Sp DEF -
Iron Defense - Double DEF -
Barrier - Doubles DEF -
Cotton Guard - Raises Defense by 3 stages ( A little more than double )
Agility - Doubles Speed -
Tail-glow - Raises S.Attack by 3 stages ( Prior to Gen V it was only 2 stages )
Those were for single stats.
Quiver Dance - 1 stage of Sp DEF Sp ATK Spd
Shell Smash - 2 stages of Atk Sp Atk and Spd, but lowers Sp Def and Def by 1 stage.
Calm mind - 1 stage of Sp atk and Sp def
Bulk Up -Atk and Def 1 stage each
Work Up - Sp atk and Atk 1 stage each
Cosmic Power - Sp def and def 1 stage each -
StockPile - Def and Sp def 1 stage each, ( This is a weird one, you can use it three times, and you can swallow it or spit it up, with those moves. )
Shift Gear - Spd by 2 stages, and Atk by 1
These are all of the stat moves that raise 2 stages of Stats or More.
Ones that I'm gonna go ahead an put in here, that I missed.
Accupressure Random 2 stages.
Curse Atk and Def + 1 Spd - 1
Dragon Dance Atk and Spd 1 each