I'll buff a move from each generation
>Constrict
Make it have a 100% chance to sharply lower speed. It's probably the worst gen 1 move in the game (excluding Splash inb4Z-Splash) and every Pokemon that learns it not only learns it at an early level, but are all caught mid to late game so most of the time, they don't even have the move, and they learn at least 10 better options by then.
>Nightmare
make it so that the Nightmare status is a permanant buff. It should persist on the mon wheter they wake up, or even switch out. As it is right now, it's just a complete waste of a slot.
>Luster Purge and Mist Ball
I'm breaking my rules here a bit, but there is no reason a signature move should be completely outclassed by a common TM. Buff both of their base power to 120. Make them worthy of being signature moves
>Natural Gift
Make it so as long as the Pokemon is holding the berry, the move can be used. No one uses Natural Gift, not even in a casual setting.
>Wild Charge
please just make it 120 base power. if you must, make Volt Tackle 150 base power as well.
>Land's Wrath
Same reason as Luster Purge, although Thousand Arrow's sis so good, I really don;t know of a way to buff Land's Wrath to make it worth using. I guess give it the Taunt status?
>Brutal Swing.
Just turn it into the Dark-type Earthquake that they obviously wanted it to be. At least then Knock Off wouldn't be the only physical Dark-type move used these days.
Gen 7 is kinda weird that a lot of the moves are good, but suffer from garbage distribution.