There are 25 Decepticon symbols hidden throughout Chapters VI-X. Find and shoot them all for the trophy. An on-screen counter will help track your progress toward the trophy. If you are playing in co-op, you and your partner(s) will earn credit toward the trophy no matter who shoots the symbols. All five of the Autobot chapters have 5 Decepticon symbols each.
Here is a list of each Decepticon symbol from Chapters VI-X (FULL credit to Mazztadawn for the list):
Chapter VI – Defend Iacon
26. Checkpoint: Iacon Under Siege
As soon as you have control of Optimus after leaving the lift, listen to the giant holographic Jetfire blab on for a bit. As you do, take a peek between his legs to see the first emblem there.
27. Checkpoint: The Broken Lift
As you get outside of the glass walkway where the Decepticon War Machine was, hop over the barrier and continue along the walkway until you see the emblem on the far right. It will be quite a ways across, sitting on a pipe – judging you, silently making fun of you.
28. Checkpoint: Iacon Speedway
Once you get past the few war machines and continue through the tubes, Bumble Bee will say” oh great! The speedway’s out!” From here, the other two Autobot’s will zoom off to the lower level. Don’t jump down just yet as the next emblem is waiting for you directly across the way.
29. Checkpoint: Central Ventilation System
The easiest way to find this emblem is to reach the circular platforms that rotate around large pillars. Before jumping over to them, do a 180 turn to the edge of the walkway behind you and look down and to the left a bit. The emblem will be right there staring at you.
30. Checkpoint: Inside the Decagon
When you enter the room that makes you realign the data streams, head up to the broadcast room by riding the large boxes that form. Once you take the ramp up to the third lift, ride the box and shoot the emblem directly across and up from you before you reach the top.
Chapter VII – Kaon Prison Break
31. Checkpoint: Courtyard
After you pick up your first weapons, head across the walkway into the next room. Clear it out and continue through the next door to another walkway. Once on it, look to the left side to find the first emblem just floating there above some wires.
32. Checkpoint: Megatron’s Ambush
As you break out of prison with your axe – because having an axe in prison seems to be ok with decepticons – head down the hallway all the way to the end and to the right you will see the emblem in a cell with some autobots. Wonder what the emblem did wrong to end up there. Shoot it with the weapon you grab in the hall and free it of its misery.
33. Checkpoint: Hangar
After you free Air Raid and the rest of the the Autobots, you will eventually come to a room that has a window in the floor and you can see a swarm of Autobots running. In the next room, after you clear it out, look out the middle window to see the Autobots hopping into dropships. Above the farthest left ship, will be another emblem.
34. Checkpoint: The Final Approach
Once you destroy the crawlers and hop out, you will come to some missile firing decepticons that are taking out the floor around you. Once you get past the second set of them, head up the ramp and the next emblem will be on the far right – plain as day, almost as if it’s winking at you, saying “hi, how YOU doin?”.
35. Checkpoint: The Final Approach
After you pass the missile firing cons, keep following the giant arrows until you finally reach the last ramp and bridge where you will hear Megatron chime in with “you’ll never leave this place alive, Optimus”. When you hear that, you are at the final ramp. Make a right before going up and find the emblem there under the bridge.
Chapter VIII – To The Core
36. Checkpoint: Omega’s Holding Cell
Just after the start of the chapter a little ways, you will pop three locks on a door and then run into some cloakers. Kill them and then head to the left of the next door you see. In the corner, across from the ramp leading up, will be a doorway with bars across it. Smash through to find the first emblem inside.
37. Checkpoint: A Plague of Corruption
This emblem is a clever girl. When you encounter your first spaceslug, you will come to two batches of metal cables. Prime’s Fist icon will show up on both, so pull it out – your axe I mean – and smash through the left batch of cables. Simply head along the walkway, jumping over the gaps and the emblem will be awaiting your arrival at the end.
38. Checkpoint: Cybertron Slugs
After a large battle, another Slug will make its appearance known. After it does its thing, hop down the hole in the floor and drop all the way to the bottom. As you land, turn around to find another door that is covered by bars. Shoot the emblem through the bars and a cut scene will start.
39. Checkpoint: Sea of Corruption
After the Slug has been saved on the bridge – you did save it, right? – head to the elevator and go for a ride down. Once at the bottom, follow the ramp down and make a right at the bottom. You will need to hop over some energon to the next rocky platform there. Once on it, look across to find the emblem in the back.
40. Checkpoint: Sea of Corruption
When you enter the area that is flooded with energon, you will need to shoot the rocks on the ceiling so that they fall and give you conveniently placed platforms. To find the emblem here, make your way to the center platform where the door is and then head to the right of it. Shoot the rocks for your path and you’ll find the emblem by a slug that is hanging out on the wall.
Chapter IX – Aerial Assault
41. Checkpoint: Attack on the Relay Station
As you start the chapter, you will need to follow the beam through some rings and tunnels. The very first tunnel you enter will be all red and molten-ish. As you enter, look to the right/center for the emblem, where a metal plate comes loose. You can alternatively keep going straight as you enter the tunnel and go right through the emblem instead of hooking left as the other Autobots do.
42. Checkpoint: Coolant Chamber
When you enter the cooling system, you will come to some sentries that are guarding a vent door that needs to be blown open, just past the control bubble. Before you shoot open the door, there is a door to the left that houses an emblem inside it. Give that opening a good barrage of bullets and collect your reward.
43. Checkpoint: The Nerve Center
Once you have made your way through the tunnels. You will come to a large room with turrets and the Pulse Regulator. Look up, way up, to the large tube that spans the ceiling and there will be an overshield and the next emblem on top of it.
44. Checkpoint: Approaching Trypticon
When you enter the large room with numerous turrets scattered about, a flood of Decepticons will enter. Clear out everyone and the Access Lift in the center of the room will rise with its orangey glow. To find the emblem, hop on top of the access lift and look to the left. Look for 2 boxes sitting on a ledge and the emblem will be cowering behind there.
45. Checkpoint: Inside Trypticon
Once you enter Trypticon – you’ll know because he never shuts up – you’ll be faced with another swarm of Decepticons. There will be tanks and Demolishers as well to make things more interesting. Once everyone has exploded into little itty bitty robo parts, head to the front of the room and take a look down into the first opening in the floor to find the emblem there.
Chapter X – One Shall Stand…
46. Checkpoint: The Threat Emerges
As soon as the mission starts, walk forward through the doorway and turn around. The emblem will be right there, above the doorway. Easy peasy!
47. Checkpoint: The Threat Emerges
When you reach the energon battery that needs to be destroyed to proceed, do so and continue down the tunnel. Once you exit, immediately look in the alcove on the right. In here, the emblem will be high up on the far wall. Be careful that you don’t go too far though once you exit the tunnel as Trypticon will trigger a cutscene and you won’t be able to return to get it.
48: Checkpoint: The Threat Emerges
When the gang falls to the ground and Trypticon starts with his bravado, head to the bottom floor and go to the far back and there will be a destroyed wall with the emblem sitting on the other side.
49. Checkpoint: The Threat Emerges
You see that large pillar in the middle of the battle arena? Sure you do. You’re probably hiding behind it. Well, go around to the other side of it to find an emblem there.
50. Checkpoint: The Battle Continues
Once you reach the second part of the battle with Trypticon, head to the far left side and you will see two circle-ish metal plates against the wall. There will be a crack in the middle with some flames in it along with the final emblem of the game. Shoot it and do a dance or a jig or whatever it is that you do.
Credit also to MrKennyKRH for the video walkthrough: