Challenge mode and ANDREI's extra monsters, with no extra health, and no extra ammo. Done. The last room was a... Let's say it was a surprise
I was almost ripping hair from my head as i managed to kill the lesser enemies from around Makron (Invulnerability + Quad Damage, thank god) with power-ups just depleted, the son of a bitch landed a nasty BFG shot right to my face. I had to fight Makron himself with just +14 health but luckily i managed to dodge everything he shot at me.
This was a truly nerve wrecking playthrough