Since the card description states that Corruptis is a Daemon Prince, my question is if the Ordo Malleus Inquisitor gets a +2 to battle score when fighting Corruptis in the final confrontation.

Nope.

Rulebook, page 12:

The scenario sheet is an enemy for the purposes of card

abilities but has no traits and is not a Threat card. It

cannot be taken as a trophy and does not leave play.

Not sure if that quote makes it a "no". It depends on interpretation. I.e. Is Corruptis an enemy and is it a Daemon? If yes, then the Inquistor should receive +2 against it (- For comparison, does the Ultramarine Captaing have +2 against Corruptis?).

Furthermore, daemon hunters have been chasing Corruptis before according to the backside description of the card.

Not sure if that quote makes it a "no". It depends on interpretation. I.e. Is Corruptis an enemy and is it a Daemon? If yes, then the Inquistor should receive +2 against it (- For comparison, does the Ultramarine Captaing have +2 against Corruptis?).

Come on man, what the hell? The quote 100% emphatically makes it no. The bit he quoted says "scenario sheet is an enemy, but has no traits." Enemy yes, traits (like Ork, Tyranid, Daemon) no. Doesn't get clearer than that.

Jorli584: It is just one of those things, for game balance purposes, the Daemon Prince Corruptis is not considered a daemon, otherwise, it is true that the Inquisitor would have an unfair advantage.

I may be wrong but I seem to remember that in the Warhammer 40K game, back a few edition, the soul grinders, which were a unit in the daemon of chaos rulebook, was not technically a daemon, even though it was a daemonic vehicle. Or something along those lines...

Sometimes, for the sake of the game, you have to make abstractions of the rules.