i think that metroid prime 2 echoes is way harder than the others, like the bosses amorbis, quadraxis, dark samus, and the last dude um... emperor ing (i think thats its name)
Metroid prime 2 was the hardest in general, which is why it was so controversial. However, Metroid Prime 3 has the option of playing the game on "hypermode" difficulty, which is far harder than Metroid Prime 2.
-Also, Emperor Ing was really the second to last boss. You can't forget about Dark Samus 3.
I liked the original metroid prime the best, after beating it like 5 times it's beginning to get old, but the music was unforgettable, and whenever you think you figured something out or you have a routine, it screwws up because something new happens.
ya echos is hard but the dark marines own me buts its good the big thing tooth thing that was possesed the dominant thing boss guy was easy you shoot him like crazy while running like an idiot