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human
[MGS1/4] How did Solid manage to use REX to actually beat RAY?

After  MGS1, the damn thing couldn't even stand anymore and they even mention that it's been sitting in that hangar the entire time up until Outer Haven went there to collect the Rail Gun. We even see it in the same sorry state as Raiden fights Vamp.

How on Earth did Solid get it to not only work, but beat a brand new MG RAY!?
gpt
1. Snake was meant to beat Liquid Ocelot and destroy the Patriots AI.
2. Snake had Otacon on his side who not only knows REX inside and out but also activated a "street-fighting" protocol in REX that used it's bulk to it's advantage against the agile RAY.
3. Liquid Ocelot was either using the modified marine RAY prototype from MGS2 or a modified mass produced version (unmanned and weaker, meant to protect arsenal gear). While Metal Gear RAYs were designed to hunt Metal Gears, there was never another Metal Gear REX. They were all derivatives/ knock offs of the original REX (best version), RAYs were never tested against an actual REX that had nigh impenetrable armor.