Gotta go with dark souls. Altho I'd say to get the first one if you can. I started with the third and it's my favorite soulsborne game easily, it is one of the easier ones in the series tho. You start off with the most refined movement and combat and there are pluses and minuses to that.

When I play dark souls I feel like it’s a game of learning and how to press the B button at the right time. It’s “hard” because death is punishing and every enemy has lethal potential. It’s brutally hard in many regards, but 99% it’s fair. I spent like 40+ attempts on some bosses learning their patterns, screwing up dodge frames. But I always said “Just one more I got this guy”. Out of the games you listed I've had the most fun and spent the most time on dark souls. Actually just rebought 3 myself on steam after playing on ps4 for years. Bought it 2 days ago and already have 11+ hours on it lol.