Wait until the credits end to face another Boss in a bonus battle.

After Ethan and Gideon are at the escape pods, Ethan will instruct you to find Olivia. You must first find and use six hidden buttons in this level. To find the first button, repeatedly hit the locker in the first room until it disappears. To find the second button, look behind the pillars to the left of where you start in the first room. To find the third button, exit the first room in the direction you entered this level. The button is located near the door with the fire in front of it. To find the fourth button, look behind the left locker in the second escape pod room. The fifth button is found behind the pillars in the second escape pod. The final button is located on a door on the first section of walkway overlooking the large room with people running below and ships flying in space above. Once the final button is pushed, simply turn around and follow the now open path to the secret tunnel. Once on the other side you can find a pipe that resembles those from the Super Mario Bros. Climb into it to warp to a Mario-style cave, where the music also changes to match that of a classic game. Jump across the platforms and reach the end of the cave. Once there you will find three more pipes. Each one of them will warp you ahead to a farther point in the game. The pipe on the left advances to the intermission sequence showing Marin, Giddeon, and Olivia taking off from the planet in Chapter 4. The middle pipe warps you to the top of a building in New Bahn. The pipe on the right warps you to the escape pod intermission sequence.

Find and use the six hidden buttons in level B of this chapter. To find the first button, when you first start destroy the black object in the wall in front of you. After you pass under a large gun and you will walk into an open area with three more black objects. Destroy the black object in the corner opposite the entrance to the area to find the second button. Then, go up the small ramp and wait until two bridges appear, on one side of another large gun. Use a charged jump from the bridge to reach a platform above the large gun to access a hidden room with the third button. Proceed through the level until reaching an area with three doors that enemies are appearing from. There should be two small doors to the right and a large door under a turret farther back (which leads to a tunnel that contains the fourth button). To find the fifth and sixth button, get to where you must use a switch to create a bridge. Do so and start crossing it. While walking across the bridge, look to the right to find an alcove with two large explosive objects in it. Destroy both of them to find the last two buttons. Note: Use the button closer to the start of the bridge first or the secret pipe will remain locked. After all six buttons are used in order, the locked door at the end of the bridge can be opened, leading to the secret Super Mario Bros. pipe.

Press [Tab] to access the type line. Enter the code as displayed to activate the corresponding cheat.The max skills seems to get stuck on once you've advanced to the next level or started the next cutscene.

The weapon codes spawn the weapon in your right hand.
Code - Result:

PulseGun - Acolyte
SeekerXJ9 - Darkfire
SeekerMicrowaveGun - Discord
Pistol - Faust
PlayersOnly - Freeze Everyone but You
SeekerLauncher - Fury
God - God Mode
Blaster - H.A.Z.E.
Assault - Kaull
Suicide - Kill Yourself
BadAss - Max Skills On/Off
Teleport - Move to Crosshair
Invincible - One-Hit Kills
Photon - Stalker
StunGun - Stun Gun
Launcher - Talmage
SeekerPistol - Talon
UseAmmo - Unlimited Ammo/Energy
XJ9 - XJ9

Press [TAB] to access the type line. Enter the code as displayed to activate the corresponding cheat.The max skills seems to get stuck on once you've advanced to the next level or started the next cutscene.