I have several casual games going at the moment. They give a range of grind. Two are idle games, which grind themselves.
One is Pathfinder Adventures, where I rejoice in the grind. The grind here is simply playing the game. Of course, that is always what grind is; I think of “grind” as when you must repeat the same content repeatedly to unlock new content or achieve some arbitrary goal. In Pathfinder Adventures, you can pay $25 for all the content, pay a smaller amount for a la carte, or repeatedly play “quests” that are essentially the same content as the main “story” but with randomized content and no cut scenes. Those award 100 gold (plus gold for enemies), where it costs 2000 gold to add a character option and 4000 to unlock a set of story missions. You use the same character set on quests with a different character advancement mechanism. Because I enjoy the quests, I have not spent any money, because I will happily get enough gold to unlock everything I want just by playing normally. It is a strange irony they are more likely to get money from people who want to play less. At some point, I will probably play through the story missions on all the difficulty settings, but “same content but you must roll higher” does not sound like a huge draw.
I am also playing Evil Defenders, a mobile tower defense game ported to PC and heavily discounted on Steam. It is mostly entertaining, but not good enough that I can really recommend it. Notably, it has a poorly balanced need for grinding, presumably a relic of mobile F2P microtransactions. Playing gives you “souls” you can spend to upgrade your towers. These are not “nice to have” but absolutely required to beat later levels. After hitting the first level where the difficulty curve spikes faster than the pace of advancement, I went back to try previous levels on higher difficulty settings to get more souls. I cannot yet say whether you need to grind for souls or just beat every level on every difficulty setting (bonus souls for each “star” on a level), but it feels grindy enough just having six difficulty settings for each level. And there are achievements tied to beating the fifth and six settings for each level, so you know my completionist, achievement-whoring heart is going there. Consulting achievements, I see that 92% of people who have bought the game on Steam have played it, much higher than Borderlands 2, but only 19% of players have completed all 15 levels. These are not long levels, the basic difficulty is 10 waves, and you could beat the whole game at one sitting were it not for the grind. More than half the players who have completed every level have also completed every level on every difficulty with a perfect score, so this game either caters to obsessive players or requires that sort of investment to beat the last level at all. Because if you need to defeat 14 levels at all difficulty levels to earn enough upgrades to beat the last level, why not make a perfect game of it?