Checkpoint 3:
This time its all out anything from Radecs side. Get rid of your Sniper Rifle, find something more suitable and stay in the same position (left stairs, upper level). Wait here and shoot at any Helghast soldiers below. They will start to come up the stairs, only one and one though. If they do, knife them to death. When things gets quieter, head down and knife the remaining soldiers. Now get that Sniper Rifle again, do the exact same thing you did with the previous Rocket-Men.
Checkpoint 4:
Finally, time to bring down Radec himself. Get to the bottom floor and grab yourself a Shotgun. Keep running constantly and when Radec shows himself, shoot. You need to constantly look for a blue light, thats where he will spawn. When you hear him talk you know that he is behind you, knife in hand charging you. Hit the sprint button and run. Turn around and fire (dont miss, his knife is deadly). At times he will not try to charge you, instead he will fire at you with his mg, just unload as much as you can whilst staying alive. Repeat, repeat, repeat. Finally he will spawn right infront of the huge gate to the north. Now, remember where you threw away that Sniper Rifle? Good, pick it up and get to the south side on the upper level. Get Radec in your sight, fire at him two times and he is dead.
Secret Trophies
Giantslayer - Kill the Heavy within 1 minute 
Kill the Blood Meridian heavy in under 1 minute
You will find the Heavy in the Blood Meridian level, Heavy Canal checkpoint. You can't miss him. Shoot his head (big helmet with lots of spikes on it), he will turn around. Rush up to him and empty your clip in his back.
Elementalslayer - Kill the ArcTrooper within 1 minute 30 seconds
Kill the Tharsis Refinery ArcTrooper in under 1 minute 30 seconds
You will find the ArcTrooper halfway through the Tharsis Refinery level, Lower Refinery Complex checkpoint. You can't miss him. Same strategy as with the Heavy. But instead of shooting his head, shoot the barrels that go on the wire above you when the ArcTrooper is close to them. He will turn around exposing flammable containers on his back. Run right up at him and empty your mag in his back (this will cause him to explode and you will probably die to if your to close, but hey you got the trophy!).
Dragonslayer - Destroy the ATAC within 1 minute 30 seconds
Destroy the Salamun Bridge ATAC in under 1 minute 30 seconds
You will find the ATAC in the Salamun Bridge level, Academy Rooftop checkpoint . You can't miss it. As soon as the battle starts, check which side the ATAC moves to. When he is in position over the fence shoot the blue lights with your rifle. The ATAC will get stunned, now quickly run up towards the stairs. there will be a Missile Launcher on the ground (on both sides). Equip it but don't fire. Now press
to equip your Pistol, aim down the sight on one of the blue lights. As soon as they regain full strenght (full light), shoot it to keep the ATAC in stun-mode. Now take out your Launcher and pop one in him. Don't wait for the reload, just draw your Pistol again. Repeat said move, now reload, draw pistol, fire on the light. Draw Launcher, fire Launcher, draw Pistol etc etc etc. if you run out of missiles there are some on the other side of the platform, just keep the ATAC in stasis the whole time.
If you are having trouble, please note there is a tunnel beneath the roof - you can easily hide in it. This video may be of help (credit
Aidan).
Demonslayer - Kill Radec within 20 minutes
Kill Radec at Visari Palace within 20 minutes
You will find Radec in the Visari Palace level, Autarch's Sanctum checkpoint. You can't miss him. This is actually not very hard, it counts from the moment you enter the room and this boss fight is divided in 4 parts (remember, if you die you dont waste time, the checkpoint reloads the time you had). I got him down on my first try on Veteran at a time of 15 minutes, plenty of extra time for just running around doing nothing.
Stick Around - Nail 20 Helghast to the wall
Nail 20 Helghast to a wall using the Boltgun VC-21
When you first get the boltgun in the Suljeva level use it alot. Try to not just fire anytime you see an enemy. Instead, try to line them up against a wall or a box or whatever and then fire so they get stuck. If you fire and kill an enemy in the open it wont count. (the pushback his pretty strong so the enemies can stand a good distance from said wall and still get nailed up).
Master Conductor - Electrocute 3 Helghast with a single burst from the VC5 Electricity Gun
Electrocute 3 Helghast with a single burst from the VC5 Electricity Gun
As you get the electricity gun after killing the ArcTrooper just use it and if you have three enemies infront of you, dont let go of the trigger button. It holds quite alot of ammo and does pretty good damage, shouldnt be to hard to aquire.
Can Opener - Destroy a Helghast APC
Destroy any Helghast APC during battle
This one will be possible to accomplish in Maelstra Barrens. Just make sure to put a few missiles in the APC (not to be confused with the tanks) when your in the Exo. The APC will be the first veichle you encounter in the Barrens.
Spare Parts - Destroy all Leech Pods
Destroy all Leech Pods in The Cruiser
In the Cruiser level, when you use the AA gun. You will need to kill all the Leech Pods (Helghan ships) before the final evacuation (friendly transports will come into vision). Just shoot every one. You have quite alot of missiles aswell, theese are heatseeking and when the red marker gets bigger it means the missiles have locked on. fire missile for guaranteed destruction. Make sure not to waste them though as it will get more intense at the very end of this section. Its much easier to hit the Leech Pods if you zoom using your zoom button.
Treadhead - Kill 30 Helghast whilst in the tank
Take 30 Helghast lives whilst using the ISA tank
You will be able to drive the Tank in the Corinth River mission. I didnt get it until the second replay though. But its pretty basic, as soon as you can enter the Tank, do so and kill everyone you see.
Mechspert - Stomp 10 Helghast
Stomp 10 Helghast with your Exoskeleton in Maelstra Barrens
In the Maelstra Barrens, just run over the enemies with your Exo, they will die instantly.