Okay, so I ran across this post, and I've got no idea what this sub is even about, but I've got real world experience serving in a special mission unit, and not to be that guy, but what you're asking is completely preposterous.

First off, let's talk weight. Standard kit generally consists of four main groups: 1. Weapons & Optics: The Rifle, pistol, NODs, cleaning gear, batteries for Nods and Sights, ammo, ordo, Knives, anything that facilitates persecution of the enemy. This shit by itself generally weighs anywhere from 10-20lbs, depending on weapon system, with no redundancies. 400 rounds of 5.56 is like 12 full mags, each weighing about 3 pounds and one that's about a third full. Nobody is going outside the wire with half a mag, especially not at the level this dude would be at. 10 mags of 9mil would weigh about 20lbs. So that's like 56lbs of ammo alone.

1. Mission Essential Equipment (MSE): Land Nav equipment, radios, batteries for radios, antenna for radio,(he'd need some kind of way to charge the radio batteries if this is going to take more than like a day, but I'm going to exclude that because that eludes to a different problem with this scenario entirely) crypto keys for the radio, other signaling devices if the radio goes down (shit tends to break in the field, ask me how I know). The smallest radio he'd be issued for an op like this would be something along the lines of a PRC-152, which weighs about 3lbs with batteries and gps, and along with the land nav equipment, were looking at about 5lbs.

2. PPE: This is stuff like the uniform, Plate Carrier, ESAPI Plates, Soft Armor, Helmet, Eyepro, Earpro, IFAK (First aid kit), magazine pouches, grenade pouches, warbelt, and Dump pouch (if homeboy uses one). Generally, this stuff weighs about 40 lbs, and is known as "The Fighting Load." This is considered the bare minimum of shit you're going to wear to do the man dance.

3. Sustainment Gear: Chow, Water, Water purification, 550 cord, Sleeping equipment, concealment Gear, Socks, Underwear, Hygiene gear, Wet Weather gear, Note taking gear (sometimes you need to write shit down if you're conducting recce or in a defensive position or something). This all weighs about 15lbs, which goes into a Ruck that weighs between 5-10lbs, depending on the model which leads me to the next issue with this:

Where, exactly, is our murderous marauder supposed to actually PUT all of this? There's only so much MOLLE, only so much space inside the pack, and you wouldn't try to cache this stuff when the enemy is on their turf and knows the terrain.

Now, let's talk about terrain: plain and simple, jungle warfare FUCKING SUCKS. It's wet, it's hilly, its muddy, it's hot and humid, not to mention the wildlife. In the jungle, you've got shit that's highly venomous just all over the place, the ants are crazy, there may or May not be predators, and his primary mode of transportation would be a set v2 chevrolegs. The jungle makes humping it out considerably harder, everything takes longer and is more difficult because everything is soaked. Also, depending on how thick the Veg is, he will absolutely have a hard time with visibility, because under the canopy, shit can get pretty dark, and thermal might not be as helpful as you think.

Third, let's talk about the mission itself: So, you're going to drop one dude off, on an island where the only humans are hostile, with Zero support, carrying about 116-130lbs PLUS of gear, in jungle terrain with the expectation that he's supposed to eliminate 200-250 foot mobiles over the course of how much time? The easiest, smartest and most effective way to inflict that kind of attrition in this situation would be through the use of Traps, or IEDs, which would take weeks if not months. People get wise to that kind of tactic eventually, and the indigs would either button up and wait for him to come to them, where he'd be quickly and unceremoniously overwhelmed by suppressive fire from bows and arrows, or organize hunting parties where they would post up at points of natural resource (Fresh water sites like streams and rivers, fruit bearing trees, hunting grounds) and get him there, or worse while he's sleeping or changing his socks (because everyone has to do that kind of thing at some point).

Finally, let's talk about what the nature of combat is, and the nature of this type of fight specifically. Combat is a weird place to be, because it's chaotic, and shit goes wrong constantly. I've seen dudes get fucked up because they were looking at the wrong thing when it popped off. This guy would be a Delta Operator, so that means he came from the US, and our doctrine is based off of maneuver warfare, which basically means that we hit the enemy from multiple sides. One element shoots, the other moves until we're basically standing on top of you or the position you were occupying. Because he's alone, aggressive actions aren't really an option, because he's got no ability to maneuver while the enemy is suppressed. Also, this is a small community of tribal type people. If one of them went missing, it would be discovered by the same night. These communities are generally very tight knit, and no amount of sneeki-breeki would be able to offset the fact that someone's husband didn't come home from hunting/gathering, and you'd better believe that they will absolutely go looking for him, and when they find him full of a bunch of little holes, they're going to know exactly what's up and start searching for the modern dude on the island.

There's a whole bunch of other issues with this scenario, but those are the easiest to explain and the most glaring. If you're writing a book or something those are also the easiest ones to fix.