CodeQuest

Note for Level 27: I could not get to the lost souls on the very top of the mountain, so I first complete this level minus those two kills, but then reload the game just before, IDCLIP to gather the final two kills, then finish the level again at 100%.

Brutal Final Doom - TNT: Evilution - Ultra Violence - Administration Center (Level 21) - 100% Completion

This is the second secret level that's access from the first secret level (level 31), entitled "Pharaoh". The exit at the end of this level goes back to the main story with level 16, "Deepest Reaches".

This secret level is accessed from level 15 "Deadzone". There are two exits in this level. The main one proceeds on with the main storyline with level 16 "Deepest Reaches" and the secret exit, taken here, goes on to the second secret level (level 32) "Carribean".

The level before this in the walkthrough is the second secret level (level 32), entitled "Caribbean". This level can otherwise be access both in level 15 and level 31.

Brutal Final Doom - TNT: Evilution - Ultra Violence - Shipping/Respawning (Level 19) - 100% Completion

Brutal Final Doom - TNT: Evilution - Ultra Violence - Lunar Mining Project (Level 23) - 100% Completion

There are two exits in this level. The main one proceeds on to level 16 "Deepest Reaches". The hidden exit (which is taken here) proceeds to the secret level (level 31) "Pharaoh".