True Ending of the Cheater Route: Vincent becomes an Incubus. Credits show him kicking all kinds of Netherworld ass, and the final clip shows Vincent with full ram horns sitting on a throne, with Catherine, and dozens of others like her at each limb, all announcing various lustful things about him and his awesomeness. The deal is sealed by the fact that Nergal IS HIS THRONE.
Made even more awesome by the fact that he took over the Netherworld in hisunderwear. That right there is all sorts of Badass.
It's notable in its own way that, after so much fumbling around women, Vincent is perfectly at ease surrounded by the other succubi, and while Catherine acknowledges they are "wrapped around his finger", he doesn't respond to their advances, merely allowing them to fawn over him while he clearly only has eyes for Catherine, who he keeps snuggled against the whole time.
Vincent's challenge to Boss/Thomas Mutton. Erica even comments on it.
Slightly before that, Boss/Thomas Mutton threatens Vincent with more nightmares for pushing the issue. Instead of backing down, Vincent threatens to stab him to death.
The very fact that he threatened to stab a god to death, and that, one would assume immortal, god was scared of him speaks volumes.
The fact that the game over theme is Sarasate's "Zigeunerweisen" is awesome by virtue.
Which is made even more awesome with the following cutscene, where Trisha, AKA Ishtar, the babylonic goddess of love, puts on her best look and "rewards" the player.
After completing the Torture Chamber (Stage 3) and the boss is dying:
Vincent: Suck it!!
Which overlaps with Crowning Moment of Funny when you remember that said boss is the infamous conjoined, lustful lovers monster.
Vincent fearlessly telling off Mutton/Dumuzid at the end of the Final Stage.
Vincent: ...From now on, my life is my own!!
Even though it was a dream and she was never pregnant in the first place, you have to give Katherine props for climbing the tower while in heels and apparentlywith child.
When continuing, Vincent will sometimes say "Now's not the time to be dead." So. Manly.
On a overall level, despite Vincent apparently not being so great dealing with relationship issues, him being a Determinator when things go wrong to the point of the other sheeps eventually looking up to him as a leader.