MISSION 22 - The Watcher On The Wall
Mission area: Costa Sud
Note: Make sure you bring or pick up a fire leech launcher during this mission (you can find one in the weapon locker on top of the outpost you start on) as it will be extremely helpful in completing the last objective.
Looks like this time Di Ravello is sending his forces at you in earnest. You'll start out on a outpost above two marked piles of cargo. These need to be protected at all costs and keeping enemy vehicles such as tanks and helicopters away from them is your number one priority. Before I go into the enemy waves I want to take a moment to cover your defensive options here. There is an AA gun mounted on top of the outpost right in the center of the walkway which is extremely useful against aircraft (duh). There is also a mounted mini-gun slightly on the left side of the area which is very good against ground vehicles and soldiers.
These should be your two go-to positions depending on the makeup of the enemy forces at the current time. You can also hijack enemy vehicles as well (such as tanks or helicopters) to use against the enemy forces, but don't try rushing them on foot as they will often go around you to attack the cargo instead. With those little tidbits out of the way, we can get to the mission at hand.
Wave 1: 2x trucks, 3x helicopters, 1x tank
Wave 2: 3x trucks, 3x helicopters
Wave 3: 4x helicopters
Wave 4: 4x helicopters
Wave 5: 3x helicopters
Wave 6: 2x jets, 4x soldiers (a few seconds later)
Wave 7: 2x jets, 2x trucks
You'll see that around wave 3 you should get in and stay in the AA gun on the outpost's upper walkway as everything thrown at you from this point on is an aircraft until the final two waves. Keep in mind that the jets will be difficult to target and you might be better off using the mini-gun or a fire leech launcher's lock-on against them instead. When the final enemy soldier or vehicle goes down, Mario will call you up to the upper walkway of the outpost to trigger a scene when you reach the marker near the gate.
The mole will be trying to escape by helicopter. Luckily we came prepared with our fire leech launcher. There's a weapon locker only a few steps away if you're in need of ammo. Get on the bike and follow him down the surprisingly straight trail until you get a lock on then blow him out of the sky with a single barrage. Guacamole. As soon as the fireball ends so does the mission.