https://en.wikipedia.org/wiki/Metroid_Fusion
Metroid Fusion for the Gameboy Advanced, the fourth installment of the series, was a return to the side-scrolling action adventure style that fans had been clamoring for since the release of Super Metroid nearly a decade earlier. Many of the same gameplay elements and tropes return. Fusion follows Samus Aran, a intergalactically renowned bounty hunter recruited by the Galactic Federation to investigate a possible outbreak in one of their research labs. As the player, you explore the abandoned vessel, find weapons upgrades, and eliminate the alien foes that stand in your way.
Fusion makes a purposeful deviation from previous games though. There she encounters a parasite know as X that has the ability to replicate the DNA of its host, mimicing and enhancing their capabilities. After making contact with the parasite she is stripped of all her suit abilities, making her extremely weak. By contrast, the parasite gains her power and uses it to hunt her down. Samus has no other choice but to hide or run from the X parasite until she discover a way off the ship. The player feels helpless. This gives Fusion a horror tone which is much stronger than any other in the series.
