As of Generation 9, the only moves that can "drastically" raise a stat are:
Cotton Guard: +3 Defense
Fell Stinger: +3 Attack if it KOs a Pokemon
Tail Glow: +3 Special Attack
Z-Splash: +3 Attack
However, with the ability Simple and a move that "sharply" raises a stat, you can change a move that's supposed to give a +2 boost into one that gives +4. For example, Nasty Plot sharply raises Special Attack (+2 Special Attack), but with the ability Simple, that will change to +4 Special Attack and will say that the move "drastically" raised Special Attack.
Here are all the moves that can achieve this (with Simple, of course):
(if the move is directed towards an a target Pokemon, that Pokemon that gets their stat boosted must have Simple, not the user)
Acid Armor: +2 Defense
Acupressure: +2 to a random stat (excluding accuracy and evasion)
Agility: +2 Speed
Amnesia: +2 Special Defense
Autotomize: +2 Speed, user's weight is halved (becomes nimble)
Barrier: +2 Defense
Decorate: +2 Attack and Special Attack to target Pokemon
Diamond Storm: Chance to provide +2 Defense after attack
Extreme Evoboost: +2 to all stats (excluding accuracy and evasion)
Fillet Away +2 Attack, Special Attack, and Speed, but loses half health
Geomancy: +2 Special Attack, Special Defense, and Speed after a charging turn
Minimize: +2 Evasion
Nasty Plot: +2 Special Attack
Rock Polish: +2 Speed
Shell Smash: +2 Attack, Special Attack, and Speed, but -1 Defense and Special Defense
Shift Gear: +2 Speed and +1 Attack
Spicy Extract: +2 Attack and -2 Defense to target Pokemon
Swagger: +2 Attack to target Pokemon and confuses it
Swords Dance: +2 Attack
Z-Ally Switch: +2 Speed
Z-Aromatic Mist: +2 Special Defense
Z-Bestow: +2 Speed
Z-Captivate: +2 Special Defense
Z-Heal Block: +2 Special Attack
Z-Imprison: +2 Special Defense
Z-Magic Coat: +2 Special Defense
Z-Me First: +2 Speed, then calls a Z-Move
Z-Mirror Move: +2 Attack, then calls a Z-Move
Z-Powder: +2 Special Defense
Z-Psycho Shift: +2 Special Attack
Z-Recycle: +2 Speed
Z-Snatch: +2 Speed
Z-Switcheroo: +2 Speed
Z-Trick: +2 Speed
Additionally, here are all the moves that can drastically lower a stat (again, with Simple):
(if the move is directed towards an a target Pokemon, that Pokemon that gets their stat boosted must have Simple, not the user)
Acid Spray: -2 Special Defense to target Pokemon
Captivate: -2 Special Attack to all adjacent opposing Pokemon if of opposite gender
Charm: -2 Attack to opposing Pokemon
Draco Meteor: -2 Special Attack after attack
Eerie Impulse: -2 Special Attack to target Pokemon
Feather Dance: -2 Attack to target Pokemon
Fleur Cannon -2 Special Attack after attack
G-Max Foam Burst: -2 Speed to all opposing Pokemon after attack
Leaf Storm: -2 Special Attack after attack
Lumina Crash: -2 Special Defense to target Pokemon after attack
Memento: -2 Attack and Special Attack to target Pokemon, user faints
Metal Sound: -2 Special Defense to target Pokemon
Overheat: -2 Special Attack after attack
Scary Face: -2 Speed to target Pokemon
Screech: -2 Defense to target Pokemon
Spicy Extract: -2 Defense and +2 Attack to target Pokemon
Spin Out: -2 Speed after attack
String Shot: -2 Speed to target Pokemon