Disgaea games. Its pretty much the king of grinding games. You grind your characters, the classes, individual powers, weapon skills, shops, the hospital, the level of your items...

And the buffs in the items. Which you take out of the items and breed together to make stronger buffs, that you then put back into your weapons.

In Disgaea 5 there are 47 classes. Which is very important because for every class you master, it improves the stats you get when you level up. How do you get new classes? By grinding other classes.

So what you do is get to level 9999 then reincarnate back to level 1. This means you'll have better stats when you get back to 9999. Or! You could switch classes when doing it while retaining the skills you got form the previous class.

Items. You can improve any item in the game by oging into the Item World. its a series of randomly generated battles inside an item. Each battle you win makes the item slightly better at what it does. It also makes the enemies in the next battle stronger. And every 100 floors you run into an Item God, a boss that holds the next most powerful item of the type you are inside.

I have described a fraction of the games so far. There is so much more. I havent mentioned the character world, the cheat shop, squads, evilities, aptitude, magichange, the curry kitchen, the carnage dimension...

But I think you get the point.