"Then go and scream Tatsumi with all the fire in your soul!!!!"
― Bulat (Akame ga Kill)
"That's not it. It's about souls. Basically, here's the story, Sid. Someone like you who's let his soul rot can't measure up by just gaining some power, not to someone with a real soul. That's not how it works down here."
― Dante (Devil May Cry: The Animated Series)
The ability to possess an uncommonly potent soul and gain highly formidable abilities as a result of the soul's power.
User has a strong soul that is equivalent to the power of many souls which comes in handy in situations that test one's spiritual fortitude and grants spiritual abilities. The user's soul is unable to be bound by anything and lives free without anything holding it back. It is also strengthened by the user's desire to get what they want, no matter the cost.
Asura (Asura's Wrath) has a strong enough soul to escape the depth of Naraka.
Ichigo Kurosaki (Bleach) possesses an immense amount of Reiryoku (Spiritual Power), signifying his unusually strong soul.
Kenpachi Zaraki's (Bleach) monstrous Reiryoku.
Genryūsai Shigekuni Yamamoto (Bleach) possesses such an exceedingly amount of Reiryoku, that he can paralyze weaker Shinigami by looking at them.
Coyote Starrk's (Bleach) Reiryoku was so powerful and uncontrolled, lesser Hollows died from simply being in his presence.
Dante Alighieri (Dante's Inferno) possessed a strong enough soul to defeat Death and traverse all nine circles of Hell to save his wife, Beatrice.
When the first flame was lit, the Furtive Pygmy (Dark Souls) obtained the Dark Soul, passing it down through its descendants as Humanity.
When the first flame was lit, Gwyn, Lord of Sunlight (Dark Souls) obtained the Lord Soul of Light, using such power to fight against the dragons and become a god to the new world.
When the first flame was lit, Gravelord Nito (Dark Souls) obtained the Lord Soul of Death, using such power to fight against the dragons and become a god to the new world.
When the first flame was lit, the Witch of Izalith (Dark Souls) obtained the Lord Soul of Life, using such power to fight against the dragons and become a god of the new world.
A Dragonborn (The Elder Scrolls) is a mortal with a soul of a Dragon, the immortal, divine children/aspects of Akatosh, the god of time.
Kratos' (God of War) soul is powerful enough to escape the Underworld more than once.
Issei Hyoudou (Highschool DxD) possesses a will strong enough to keep him pushing towards his limits and is powered by his perverted mind.
Brook (One Piece) projecting his own, powerful soul, incapacitating an army of Big Mom's homies due to them possessing weak souls that aren't their own.
Prometheus, Zeus and Napoleon (One Piece) were created from Big Mom's own soul, making them the strongest homies among her collection.
Kazuma and Ryuho (s-CRY-ed) possess a strong, independent spirit, driven by their need to live without being controlled by anyone or anything.
Witch Souls (Soul Eater) are known to hold great power, making them a sought after prize to meister, weapon and kishin alike.
Frisk's (Undertale) soul is matched and fueled with determination.
The souls of all Saviors (Seiken Tsukai no World Break) are strong enough to survive eons and then reincarnate retaining memories of their old lives and their perspective and superhuman or magic abilities...
...Moroha Haimura, in particular, has a far powerful soul compared to other as it survived two lives in its third life being called an Ancient Dragon retaining his superhuman and magical powers.