Putting the cart before the horse again.
My player is fighting the same enemies from the start of the game?
Better stop that, or make them more powerful.
No. Wrong impulse.
Step back and reconsider. Why not make the path he'll take anyway the right one?
Why is he fighting these enemies?
Why is he in Lvl 1 land grinding Rats when he should be at the castle of the dark lord felling dragons?
- He likes doing it. Nothing you can do will stop him.
- He's trying to have some time with the game that day without having to do anything High risk yet feel he is still making progress, because he's having a rough day IRL? Why not let him.
- He likes Steamrolling things? Once again, Some players like every combat to be difficult, others just like to Plan/Research/Build that perfect Endgame build early on and grind to blow through everything.
- He thinks he needs to because a boss face-stomped him.
- He's grinding Crafting Materials that only drop there?
- He forgot how to play after a hiatus and wants some time to get to know the game again?
- He want to test out some skill combination/ Party build in a stress free environment? Sometimes you need a practice dummy.
- He's lost the main plot and is just lost.
- You've put the lvl 1 debuffer/Buffer/Healer enemies along side contemporary enemies? Go you, good encounter design.
- He lost to a boss and wants to blow off some steam?
- He just reached the final boss, and wants to go feel like a god for ten minutes?
- He likes the area and wants to be in there just a bit longer
- He literally needs 10 xp for the next level and was in the area anyway.
- Completionism. Completing that Bestiary, leveling all the characters/Classes.
Now, you are the creator, and as such you should decide what kind of game you want to make.
Just as the player will decide if it's worth it.
But in the large list above, some are player choice ( I just need to unwind by killing some ****ing rats, man) and some are design flaws (I don't know what else to do), and some are design choices. (Multiple classes/party members to grind)
I think we can at least agree grinding caused by design flaws should be eliminated.
The player thinks he needs to grind to defeat the boss?
Have you tried just telling him what level he's supposed to be? Because I believe a player needs to know the difference between 'Hard because Hard' (lvl 50 dragon in a lvl 50 area), Hard because I'm not supposed to go here (Lvl 80 enemy in lvl 30 area) and yes, I am supposed to grind just a bit (Lvl 50 dragon when the player is 45).
Does this mean all equally levelled enemies are equally difficult? No. The a lvl 50 dragon is harder than the lvl 50 bat, but I'm supposed to fight both at lvl 50.
A bit Handhold-y? Maybe. But it is at least a solution to some of the reasons why players grind, like not knowing if they're even supposed to go there, or not knowing of the fight is supposed to be hard or they're under leveled.
It also means players can intentionally gage how much they want to grind. Some players want to do the lvl 50 fight on the minimum level they can.
Others want the fight as intended, and do the fight at 50.
And some just want to plow over it, but at least now these last players at least get it rubbed in their face that they chose the easy option out.
Because grinding isn't a problem in itself, enemies becoming irrelevant isn't a problem on it's own.
Trying to eliminate grinding by making grinding harder isn't the solution.
TLDR: Why is my Player grinding and am I all right with some off these reasons? What can I change to make sure he doesn't want to grind anymore in ways I would rather he not? Think of why your player grinds.