The canyon stage really hurts. One of the boulder sections forces you to either abuse the boulders' broken hitboxes or glitch them out of existence with the camera. The second instance of the miniboss is practically unkillable without the sword or the strength upgrade, so I was initially forced to just "climb" over him while taking damage and then run to the other side. Hitting the edge of the rail in the second minecart section sometimes dropped me into a pit despite making the collision sound. To top it all off, the harpy boss at the end became invincible after her health bar was drained. (The cutscene was funny though.)
The game could benefit from more tuning in general. Player error allowance is often lower (or occasionally much higher, as in the case of the completely nonthreatening axe-throwing goblins) than it should be. The game gets hard very quickly and seems to expect you to buy stuff from the shop, which essentially requires grinding and replaying stages. Magi's jump arc is a bit off from the Mega Man-styled physics I know you were attempting, as she just sinks like a rock the instant you let go of the jump button.