I always felt the big bad guy at the end of the game never truly knew what was happening until the moment the hero stepped on his throne room.

The way we, the player, manage to go all the way to his chamber relatively undisturbed kinda hints he didn't know we already killed thousands of his soldiers and he should be afraid, very afraid.

Surely, if he knew we managed to destroy the Omega Tank, the Destructoid, and the Terror League all by ourselves, he would take better measures than just putting on some armor and some guards at his door.

So nope, he probably never truly knows what is going to hit him, or maybe he really overestimates his abilities.