Endgame

"I thought I told you this was a one-way trip!"

"Looks like it still is...they'll be looking for us you know..."

"Nikolai, we gotta get Soap outta here..."

"Da - I know a place."

- Captain Price and Nikolai at the end of the level.

Endgame is the final level in Call of Duty: Modern Warfare 2. Your objective is to kill Shepherd before he can escape.

Walkthrough
You begin the level in hot pursuit of the traitor, Shepherd. Get into a speedboat and chase him down through the cave and down the river, with you driving and Price firing away. Along the way, OpFor will be taking potshots at you and Shepherd. Price will gun them down, but you can return fire while driving with your Mini-Uzi. Don't be afraid of losing Shepherd; his location will be marked on your HUD.

Continue along the river while keeping your target within your line of sight. At one point you will need to go through a long cave, and once out you will be in an open area filled with rock formations, enemies in boats, and even a helicopter. Be careful not to take too much damage, and don't crash into anything!

After a while of intense fire, you will eventually hit an area filled with rocks and rough water. The ride will get a little bumpy here, but you will eventually meet smoother water. Continue your pursuit and eventually you will hear a conversation between Shepherd and his ride out of the area: a Pave Low. Once the chopper comes and extracts Shepherd from the river, Price will tell you to steady the boat. Once he gets a clear shot, Price will fire and the chopper will come crashing down. But it's not over yet.

After your "victory," everything seems to be over...until you realize that you are heading for a waterfall. Price tells you to back up, but it's already too late; you both plunge into the water.

After a brief period you will wake up. Hurt, you reach for your knife and get back up with the intention of killing Shepherd. There are two soldiers, but they pose no threat to you (One will try to shoot you but has run out of ammo). You will walk towards the downed Pave Low (in a very unbalanced manner) and before finishing off Shepherd you need to eliminate the injured hostiles. Shepherd will stumble out and run in an attempt to escape. Follow him and you will see him leaning against a car.

If you spare him for a moment, Shepherd will tell you to go ahead and kill him, although it won't change anything. If you hesitate a bit, he says that he knew you couldn't do it. He then comments you on being a good warrior, but claims that you couldn't take that extra step to do what was absolutely necessary.

However, once you attempt to stab him, Shepherd will block your attack and stab you himself.

Before you wake up, you hear Shepherd stated that the world watched as he lost 30,000 of his men five years ago. When you come to, you find him loading his .44 Magnum Revolver in preparation for your execution, saying that "tomorrow there will be no shortage of volunteers or patriots". However, before he can kill you, Price attacks him and saves your life. They will now be locked in a fistfight while you reach for Shepherd's pistol. However, he stops you just as you are about to get it. They once again return to their fight, and although they seem to be equally matched, in the end the brawl shifts to Shepherd's favor.

Soon you will notice that the knife Shepherd stabbed you with is still inside you. Pull it out, and once that is done you must aim and throw that knife at Shepherd. Your objective is complete once that knife enters his head.

Eventually, Price will wake up and come to your aid. As he attempts to heal you, a helicopter will arrive. It is none other than Nikolai. This is a play on Price's words before the entire Operation that this "was a one way trip'. As they help you towards the helicopter, they realize that the rest of the Shadow Company, as well as the US military and Task Force 141, will be looking for them. However, Nikolai claims that he "knows a place..."

Trivia

 * The player is once again playing in a wounded status, just like Call of Duty 4: Modern Warfare. At first, walking with severe injuries, like in "Aftermath", and then playing while lying on the ground, like in "Game Over". And, also like the first game, Soap is the one who kills the main antagonist, and is saved by a Russian.
 * An MH-53 Pave Low has three engines, and will not go down if one is destroyed, which is most likely the target Price was aiming for.
 * After Shepherd puts the round(s) into the cylinder, he cocks the hammer, which spins the cylinder clockwise (from the player's perspective). As he attempts to fire at Soap, the cylinder spins counter-clockwise (as if an un-cocked double action). Not only does the cylinder spin the wrong way, but the round should have been fired the second he pulled the trigger.
 * If the player doesn't get close enough for Shepherd to attack them, he opens a conversation with the player. He says: "You know what they say about revenge... you better be ready to dig two graves... Go ahead and end it. It won't change anything... Hmph... I knew you couldn't do it... You're a good warrior... but you could never take that extra step... to do what was absolutely necessary".
 * The above quote is a reference to one of the many quotes that appear whenever the player dies: "Before you embark on a journey of revenge, dig two graves. -Confucius".
 * No matter where the player aims with the throwing knife, it always lands in Shepherd's head.
 * It is unknown where the player gets the Mini-Uzi from, though it may have been on the boat. However, if you start the mission directly from the main menu, it will give you an RPD and a Mini-Uzi. Although the RPD is nearly useless because you can only fire it at the beginning of the level and eventually you lose both guns.
 * "Endgame" is a synonym for the phrase "Game Over", the last level in the first Modern Warfare.
 * No matter how fast you are to crawl to the .44 Magnum Revolver it will always show Sheperd kicking it away, leaving you with pulling out your knife and using it as a Throwing Knife.