Tariq Abdul Lateef

Lateef is the scientist employed by Al-Khalifa to verify the integrity of the DNA that's being offered for sale. When he arrives at the casino, he'll immediately head into the western elevator and go straight to room 803. He never leaves, so if you want to take him down, you'd best do so quickly, or pack a sniper rifle to take him out.

Strangulation

As mentioned, Lateef gets into the western bank of elevators when he arrives. If you get atop the hatch there before he gets in, it's a simple matter to strangle him and steal the payment suitcase.

You can also snipe Lateef from room 703, but make sure you hit him, or he’ll see you and alert the guards.

Sniping

Apart from the strangle kill, your only real chance here is to snipe Lateef from the seventh floor. Luckily for you, he never leaves his room, 803, allowing you to easily snipe him from 707, either after killing Schmutz or waiting for him to leave the room. Note that allowing Lateef access to his room in this manner, without stealing the payment briefcase from him on his way up the elevator, means that it’ll effectively be impossible for you to get, unless you’re willing to make a frontal assault against the five or six bodyguards that guard the room.

Of course, there’s a messier way to take out Lateef that may save you the trouble...

Bombing Run

You’ll note that there are plenty of fire alarms on the seventh and eighth floors of the building here. If you want to make a mess of Lateef & Co., then you can leave some kind of briefcase with a bomb in it in the lobby outside the elevator doors. Assuming that neither of the cops there make a beeline for it to pick it up, you can leave it there and and pull a fire alarm, which will send Lateef and his bodyguards streaming towards the elevators. (Don't they know you're only supposed to use the stairs?) Detonating the bomb while they're milling about will take down your target with no need to get up-close-and-personal.

Al-Khalifa

As mentioned, Al-Khalifa takes up residence in the VIP Lounge as soon as he enters the hotel, making no stops anywhere else. Getting to him will be difficult, since only Schmutz and the waitstaff are capable of getting past the guards. Waiters must be empty-handed, and will be frisked when they pass the guards, so that doesn't help much. Schmutz (or 47 when he's wearing Schmutz's outfit) can get past the guards with a suitcase (and only with a suitcase; if he shows up empty-handed he'll be turned away), but he likewise won't be able to carry any weapons under his clothes.

Thus, Al-Khalifa is one of the toughest targets to kill in the entire game, whether you're trying to do it quietly or just get it done, period. There are a few ways to kill him, however, without bringing on too much trouble on yourself.

Bombing

Schmutz is here to make a deal, and a deal will indeed be made if you let everything play out. Schmutz begins the level in the casino, then heads up to his hotel room to check on his DNA Briefcase, then returns to the casino to ensure that the sheik has arrived, then finally returns to his room to pick up the briefcase and make the exchange with the sheik. If you don't kill him or Al-Khalifa ahead of time, then you can use this pattern to your advantage and have him become the unwitting agent of a messy death.

How? Simple. Kill a seventh-floor waiter, such as the one smoking on the balcony, and grab his keycard; that'll give you access to Schmutz's room. Use the keycard to enter 707 and plant a bomb in the DNA Briefcase. When Schmutz finally does pick it up and take it down to Al-Khalifa, you can wait for him to get right up close, then blow them both straight to hell. Your suspicion ranking will likely spike all the way to the top, but this doesn't mean that any guards will start shooting at you. Just make your way to the exit as quickly as possible (assuming you've killed Tareef ahead of time) and you'll be fine.

Strangulation

If you kill Schmutz and steal the DNA Briefcase and Schmutz's outfit, then you'll be able to make the deliver of the briefcase to Al-Khalifa himself. Just dress up like Schmutz, grab the briefcase, and bring it downstairs to the VIP Lounge.

After you reach Al-Khalifa, there's a short cutscene, followed by a small pause during which he'll continually look to the south, regardless of where you look. The key thing to remember here is that none of his guards actually have eyes on him at this point, so if you act quickly, you can run behind him, bring out your fiberwire, and strangle him. With that done, get the hell out of the VIP Lounge, and if you're lucky, no one will stop you, and no one will notice the body before the courier arrives a few minutes later. This is risky, though, since you're in a hornet's nest of guards.