Little is known about Kell. He is an expert marksman, who approaches his job with cold-blooded, level-headed professionalism and is talented enough to snipe the pilot of any land vehicle, from a truck down to the mighty Chinese Overlord tank. He is also a master of camouflage, who can remain unseen to the enemy, breaking cover only to take the shot.
Under Rodall Juhziz, Jarmen Kell is further trained to be able to plant explosive charges onto enemy structures.
Regular infantry is helpless against Jarmen Kell. While his ordinary sniper rounds bounces off vehicles, he is periodically able to fire a shot that could disable them by killing the crew. The player then has the option of using any infantry unit (including Jarmen Kell) to send it to the disabled vehicle, placing that vehicle under the player's control. This can even be used against enemy construction dozers, giving the captor access to American or Chinese technology. Kell could also garrison buildings undetected, giving GLA commanders an advantage in urban warfare.
Under Rodall Juhziz, Kell is able to infiltrate enemy bases and place demolition charges (both timed and manual) on enemy buildings much like his American nemesis, Colonel Burton. Kell is very useful as a scout, as he has a wide sight range and is not often detected by the enemy. He can also mount a combat cycle for a speed boost, retaining his basic sniper rifle and his pilot-killing ability. Although vulnerable to base defenses, he can snipe out soldiers within a Stinger site, then let other units destroy it, or let allied aircraft through.
On the other hand, enemy forces could quickly trace any shots fired back to Kell and apprehend him with anti-infantry units (Kell was as soft as any other infantryman in this respect). He had to be very careful to sneak past stealth-detecting units and base defenses. One such particular rival, other than the opposing commando Colonel Burton, proved to be American Pathfinders. Their training enabled them to spot enemies using stealth techniques, while remaining hidden themselves, and their sniper skills were almost a match for Kell's.
American sentry drones were a particularly good counter to Kell, as he was both weak against vehicles and the drones were unmanned. Air units could easily take him out without fear of retaliation, provided he was not stealthed. King Raptors could detect him and kill him if he was standing still. If he is detected inside a structure, letting infantry garrison the structure will force him to leave it, and blow his cover for a while.
You have failed to learn even the first lesson of counterinsurgency Danko. Never create a martyr. - Jarmen Kell to Danko(src)
The Soviet sniper Natasha Volkova uses a functionally-identical rifle and also has the ability to snipe vehicle crews.
Curiously, though perhaps an unintended glitch, Kell's sniper rounds are able have an unexpected effect on firebases, as about three rounds could destroy one of them. This is probably because Kell's sniper rifle would kill the Fire Base's crew (spotter, gunner, etc.). As defensive structures cannot be captured, they are simply destroyed.
The Sniper Attack ability icon is actually aiming an enemy on a building's roof, but Jarmen Kell cannot snipe infantry garrisoned in structures.
Jarmen Kell is the only hero who appears in the campaign as an enemy:
In the mission Nuclear Winter, it is possible for Jarmen Kell to be killed (or at least severely wounded) by flushing him out of the building he is in.
In the mission Black Gold, Jarmen Kell will hide on a small hill near the oil fields, GLA enemy will rebuild him if he is killed.
In the mission Hidden Agenda, Jarmen Kell is near Prince Kassad's main Command Center.
In the mission Burning Skies, Jarmen Kell will be among the second wave of fleeing enemy, he must be sought out and killed or the mission will fail.
If the player uses Jarmen Kell to hijack a disabled vehicle in the original Generals, the player will not be able to recruit another Jarmen Kell as the game still considers him as alive, and the player has to let that Jarmen Kell-driven vehicle be destroyed in order to be able to recruit another Jarmen Kell. In Zero Hour, the player can recruit another Jarmen Kell if he has been used to commandeer a disabled enemy vehicle. The same also applies to Colonel Burton and Black/Super Lotus.