Metal Gear Rex, hard as shit until you realise to throw shit tonnes of endlessly spawning
Chaff grenades, then stinger the fuck out of Rex.
Fun facts I discovered: you can kill guards with
chaff grenades if you use enough of them (I would equip the stealth camo and hold the grenade directly inside a guard's body.
Save
your chaff grenades by shooting out the security cameras for good, or breeze through the Ocelot battle by capping the moustached gunslinger when you see him move from behind a pillar.
You can disrupt CCTV cameras with
a chaff grenade or crawl around in a cardboard box.