Mega Man X

Completed Mega Man X.
What surprised me after Mega Man X4 is that although you need to figth the bosses again, it is not a gauntlet. Instead, they are spread organically through multiple stages, and you also have unique bosses to figth along the way. The spider boss is difficult, but I’d say fair, after you understand it’s gimmick: it can only get to you if it has a path on the “ladder”. The “sleepy face” boss that throws its eyes at you is less fun, as it has this one-hit-kill spikes mechanic, and the “nose” has a bounce mechanic.
And by “TRex” boss I ran out of most of my ammo, so I was just throwing shit at it.
Sigma fight is three stages, but at least you start it with full health and energy tanks. First phase is the dog, which is easy. Second phase is Sigma jumping on walls, and it’s tiring, because you need to be very precise, and constantly walljump. Third phase is the wolf form, which is cool, but also random, akin to last form from Mega Man X4. Sometimes you just get unlucky and will be blasted by the plasma balls over and over, which are extremely hard to dodge.

I’ve heard some complain that this game is too easy.

In my opinion, it’s reasonably hard. You still need to know what you’re doing and be very intentional about it, and some jumps are quite ridiculous, but it’s doable even with someone bad reflexes as I am.