Mega Man 9 was hard. Admittedly, I didn’t put that much time into it, but the bit of time I spent with it made me feel more anger than enjoyment. I felt that way too much of that game came down to trial-and-error alongside surgical precision to the point where it wasn’t fun.
With that bad experience fresh in my mind, I immediately went into Mega Man 10 with the difficulty set to easy. 2 hours later, I was watching the end credits roll without having broken a sweat.