Animal Crossing, for sure.
New Leaf and New Horizons are the most relaxing because the villagers are the most mellow and I honestly think it's tougher for the OG and Wild World to be as relaxing due to the low-poly graphics.
Nintendogs on DS and 3DS are quite relaxing for the most part.

The streetpass gardening game was really nice and peaceful. Switch 2 needs more streetpass.

RENT A HERO NO 1

It's just a cozy weird game. In a small but detailed world. It's it's Similar to Shenmue in some aspects. You even get to square off with Segata Sanshiro!

Harvest Moon comes to mind. The very first one on SNES. Never played any of the sequels. I tried Stardew Valley, but that game got just too much content, I couldn't wrap my head around it. I know that's a crazy complaint, but I do seriously lack time to play video games at the moment. But my son is already 11 years old. He should get more independent in the near future so I can finally invest more time in gaming. =D

Now that I think of it, Euro Truck Simulator 2 is also a great example.

Oh yes, ETS2 was very cosy. I played it with the radio mod to get local (internet) radio stations for the part of Europe I was driving through. Thus listening to night and morning shows from all over Europe with the 6 hour time difference. Morning commute traffic report in German, Italian music over the mountains, British night radio talk shows.

It was very relaxing to climb into the cab of my Volvo truck and do some long hauls across Europe at the end of a stressful day.

I didn't find Harvest Moon (SNes) relaxing, I thought there was too much hurry (in game turns) and pressure to get things done. Barely got wife pregnant by the time it ended! I think it would've been more enjoyable if the game lasted 2-3 times as long as it did.

What was the most horrendous thing that you've done in the game?  Gone on a serial-killer sort of rampage until the cops blow you away?  Send the hooker off a cliff in your car after she does her job?   

Or have these games made you disgusted at violence and want a gentler life?  

I thought the topic were with games with no challenge or fear of death lol

Nah, I didn't say anything about challenge. More of the feeling that it doesn't matter, like death can happen but it's not an issue the game continues along anyway, like in Divinity OS you can spend 40 minutes or more in a battle but your not stressed about loosing. 

Finished Hogwarts Legacy and clearing up side stuff now, it's sooooo damn cosy. Just a natural sense of easiness in the world. I was weary of this being a kids game or kid focused but so glad I picked it up cause it's more of a game aimed at now aging fans first and probably their kids second. Just a real laid back game and doesn't sacrifice challenge in combat to achieve that feeling. I'd recommend this game to anyone on the fence or not familiar with Harry Potter, it stands alone. Even if you'll have to put up with the, rare slight cringe every now and then.