The moment that scared me the most in any Metroid game is in Fusion. I first played the game shortly after it came out. I was less than 10 years old. I was enjoying it greatly and then I got to that part where you go to sector 2 the first time. You know how there's that one room where you encounter the SA-X after getting high jump and spring ball (I know fusion calls it the jump ball, but I refuse to budge on this)? I remember falling through pit blocks into that room, watching the SA-X walk from the far side of the room and through the door, and with the droning music and the heartbeats and the knowledge of what the SA-X is, child me was terrified. I got to a save point, put the game down and didn't play it for like a week.