I don’t necessarily agree with the sense of accomplishment part. Maybe I just need to keep playing and gitting more gud, but half of the time I feel like I got lucky when taking out a mini-boss. And I in a sense proved that to myself last night against purple dude. After finally beating him once, it took me 3 more hours to be able to beat him in back to back attempts. When I finally did that, I felt the accomplishment of finally and truly besting him. And that felt better than many of my previous wins against him. But the thing is that the real mini-bosses and bosses don’t respawn and there’s no mode to replay them. So more often than getting that sense of besting an enemy, I’ll win based on a combo of me playing solidly enough, but also along with the computer rolling out less of their OP moves and more of their moves that leaves them open. The fact that many of the times I finally beat a mini-boss doesn’t just hinge on my own skill, but also on them messing up/playing poorly, takes away from the rewarding feeling.
Contrast that with another difficult game I’ve played recently, Celeste, and in that game I felt that as the deaths accumulated, I actually was improving. And not necessarily just for that one situation/level, but just overall improving on my grasp of the game. That felt more rewarding.