Powerful PCs = using more fun monsters

You never know what players will do with two gallons of mayonnaise per day until they have it.

Sometimes you just need to apply mayo to the barbarian so they have a crispy crust when seared.

Other times your want to fill someone's desk drawers.
I've got an upcoming game. I'm stealing this. "Ring of infinite mayonnaise"
- You don't have to steal it if you use DnD, the Alchemy Jug already does this and is likely what they're referring to.

Welcome to nethack, where even scrolls of genocide (removes entire monster classes upon reading) are considered to be not overpowered.

Does help that the things you can genocide are less nasty than the things you cannot, and you don't want to be facing 100% the things you cannot genocide. Amuses me even more that the best use for scrolls of genocide is to read them while confused, which causes specific monsters to be summoned on demand
- Do not read a scroll of genocide while confused.
  
  It will genocide the player race, which is generally a bad idea. You want to read a cursed scroll instead.

Giving your monsters magic items so the game is in a contant powercreep snowball freefall

Elden Ring

I wish my players would remember to use their cool magic items.

If it doesn't do direct damage, it gets stuffed into a pocket and is never seen again.

Treantmonk's Guide to Wizards and part 2 is a good guide for how to play wizards that can be ridiculously OP without directly doing much (if any) damage.

We broke the Anima system in half with overpowered characters. Not that it holds together very well normally. One mage character boosting the tank's strength high enough to lift a mountain and creating him a giant tungsten lump, another mage opening a portal directly above a bad guy's tower, apply tungsten to tower at great speed. No more tower. The GM was too amused to be mad that we wrecked his whole plan. We used the same trick to launch a necronomicon into the sun (or near enough). Also so many magically created artefacts, creation mages are just bullshit. But I got away with it because I made some for everyone.

As a GM this has always irritated me about other GM's complaining their players are too powerful. My dude, you're literally omnipotent. Your players cannot be too powerful, because you are all-powerful. Just throw bigger baddies at them. You only have to worry if one player starts getting way more powerful than the rest of the party. Then you either have to make sure everyone is cool with that asymmetrical dynamic or buff everyone else up to their level. But a party cannot be too powerful, it's just a lack of GM creativity. /rant

Edit: Dear GMs, downvoting this won't make it less true. Relax your grip on the narrative and you'll be surprised how much more fun everyone has.

A party can definitely be too powerful for the narrative you want to tell. If you've got a specific story with specific challenges in mind, then players can have abilities that can render those challenges moot.

Using Pathfinder as an example, but this would apply to several related systems too: You have some kind of ravine or other traversal challenge. Prior to gaining access to fly, the players need to use their skills to find whatever solution you've seeded into the world or come up with some creative solution you haven't thought of yet. After gaining access to fly, they can simply fly across, nullifying the challenge.

All this is to say that in certain systems, it's not simply the numbers but the nature of challenges that change as you gain power. A high-level party tells different stories than low-level parties (this isn't an accident, it's a feature), and if that's not the kind of story the GM wants to tell, it can be a problem. Arguably, however, that's something the GM should have been aware of when going into a system like DnD or Pathfinder and been prepared to raise the stakes to entirely different kinds of challenges.
- Arguably, however, that’s something the GM should have been aware of when going into a system like DnD or Pathfinder and been prepared to raise the stakes to entirely different kinds of challenges.
  
  Which is the point I was going to make! I still say it's on the GM to properly calibrate the story and/or player powers in the scenarios you outlined but overall I agree with you. I just think if a GM is trying to tell a very specific story/narrative then they should outline when each power rise occurs but that enters into railroading imo. Which at that point my advice would just be to write a book if they want THAT much control over the narrative since the players would have very little agency to alter the world around them. That's just not fun for most players I've ran games for, they always want that extra agency to get wild and as a GM it's always fun to see the unexpected and it keeps me on my toes.
  
  GMs! Let your party be powerful if they figure out creative ways to achieve that power! It's more fun for everyone!

I'm working on a Tome of Forbidden Spells just to see what my players will do with weird magic

Just gonna leave this right here....
- I was thinking more jokey. Not necessarily creepy, just weird. My plan was to make rules for all the weird meme spells like Greater Baja Blast

I suspend the tarrasque between dimensions to incapacitate it and prepare to create a post-scarcity society based off its infinitely replenishing flesh, blood and bones.

Wow, all this wonderful discussion off a silly meme, it warms my heart. Happy gaming everyone, just remember as long as everyone is having fun (GMs too) you're doing it right.

For me, balance issues are never the party vs. the monsters. I can tweak the monsters to make the encounters more challenging. Players want to feel powerful! Give them the tools over time to build the character they want to build.

It's power disparity within the group that has always been the biggest problem. If you have players that are very knowledgeable about the game and know how to build optimally, other players may feel like their character isn't good at anything because the more purposefully built characters will seem to be able to do so much more.

I usually have to balance that with custom feats or items to even things out. Disallowing multiclassing in 5e in my new campaign also helped. Too much front loading that encourage dips for the sake of dipping.

The coolest magical items don't "break the scaling" anyway, because they do cool weird stuff, rather than just giving you spells or numbers.

My players need golf bags and caddies for all the shit they have. I love handing stuff out. It's fun.

Dragon Ball Z mechanics.

Powerful PCs = using more fun monsters

Do not read a scroll of genocide while confused.