Many of the Souls that Soma dominates gives him awesome powers. Aguni (turning the floor into a wave of fire), Frozen Shade (making giant shards of ice shoot up from the ground), and Gergoth (shooting a massive laser beam) are just a few.
Some of the Guardian souls are this as well. Having a monster ally can have a lot of pay-offs, and can also feel pretty awesome. Particular shout-out goes to the Alura Une Soul, which is known as "Sweet Jail", and has Soma guarded by an affectionate Alura Une while she thrashes her plant tentacles at surrounding enemies, dealing a surprising ton of damage.
The Mandragora Soul is pretty spectacular too. Just chuck one at an enemy and watch it obliterate. Like the Alura Une Soul, it can dish out a substantial amount of damage, making it ideal for use against Menace.
After Dmitri spontaneously dies during his battle with Soma, and his soul is absorbed by Soma, he later is released and possesses a doppleganger to gain a new body. He then explains he did it so he could touch Soma's soul and copy the power of dominance.
When Soma meets Dario Bossi for their second fight. Dario has fused with a powerful fire demon to become insanely powerful. Soma tells him "I will show you why you can't be the new dark lord." He then (if you're going for the good ending) proceeds to go inside the mirror to defeat the fire demon Aguni, completely removing all of Dario's power. Owned.
Of course, there's also the worst ending, where Soma goes along with the villain's plan and becomes the new dark lord. She starts to give a Bond villain speech about how she's won and he's done exactly as she wanted, and he tells her to shut up and kills her.
The fact that, for once in the series, a bad ending unlocks a game mode, serving as a continuation of said ending.
Julius Mode in general is awesome incarnate. Take the expansive castle of the base game, add in Yoko and Alucard for a Dracula's Curse-esque ensemble, mix in triumphant reprisals of Beginning, Bloody Tears, and even Dance of Illusions, and you've got a recipe for one hell of an Arrange Mode.
Hacking the files reveals that Dark Lord Soma also has one of these for Hammer: "Kurugaii... ningen me!" (in English: "Come... you damn human!"). Apparently, he didn't have the decency to remember Hammer's name. You can hear him say it, though if you look through Voices in Sound Test.
In the true ending, it's implied that he can lead a life of peace by his continuing to reject his status as Dracula.
Furthermore, recall how Mathias seems genuinely hurt in Lament of Innocence that Leon turns down ruling the world with him. His own best friend, and by this point, his very LAST friend, has rejected him and refused to stand by his side in his endeavors. Cue the Sorrow games where everyone repeatedly stands by Soma, and only fight against him during the Bad Ending out of genuine care for him. Lament remarks what a boring, lonely existence being a vampire is, yet both Sorrow games show Dracula as Soma finally finding a place to belong once more.
