Hellaverse

Charlie (Charlotte Morningstar). A princess of Hell, the daughter of Lucifer and Lilith. She sincerely believes that sinners can be redeemed, and opened the hotel to that end. She's very kind, optimistic, and sometimes naive; she's deeply affected by violence and purges. At the same time, she's not afraid: she follows through on her vision. She sings a lot—it's her way of coping with her emotions.
Vaggie (Wagata). The hotel manager and Charlie's main supporter. Hot-tempered, blunt, and in control. She's distrustful of dangerous types like Alastor and can't stand Angel Dust. As a former angel exorcist, she knows how to fight and isn't afraid to make tough decisions. Protecting Charlie is her top priority.
Alastor (Radio Demon). He acts like a charming master of the situation: he smiles and jokes, but behind this lies immense power and a penchant for manipulation. He loves chaos and spectacle, and also plays on deals. For him, it's all entertainment, but he actually helps the hotel because he's interested in how it all ends.
Angel Dust. Hyperactive, brash, and provocative, he's not as cynical as he seems. He wants to believe he can improve, though he pretends not to care. He's very agile and quick in combat, but acts impulsively. He has a pet catalost.

Husk. A cynical, grumpy bartender who's always dissatisfied with everything. An alcoholic and gambler, he sold his soul to Alastor—and now it really pisses him off. He seems rude, but over time he shows he's not completely heartless: he can be supportive when needed.
Niffty. Hyperactive, obsessed with cleanliness and order, but also with sadistic tendencies. Very energetic and unpredictable: she can simultaneously mop the floor and punish someone.
Lords of Hell (VVV and others)
These are precisely the “strong” characters you asked about: they have real power and their own empires in Hell.

Vox. The master of media and electricity, Alastor's main rival. He controls everything through technology, loves to be visible, and manipulates the narrative. He's a narcissistic, boorish, and foul-mouthed strategist. He's a cold strategist, but he's ambitious and driven to dominate. He's terrified of Catalaster. For example, when he saw Catalaster behind him, he jumped into Velvet's arms. It wasn't because of his power, but because of the ugliness of this being.

Valentino. The king of the entertainment industry and Angel's boss. Cruel, domineering, selfish, and disregarding others' feelings. In battle and in business, he wields authority and fear.
Velvet. The ruler of fashion and social media. Bold, impulsive, loves trends and attention, acts quickly and aggressively. She often acts like a teenager on steroids, but that doesn't make her weak.
Carmilla Carmine. She owns the weapons industry and is very calculating and pragmatic. She doesn't get into conflicts without cause, but when necessary, she strikes with precision and force. She respects strength and results, not empty words.
Other notable characters
Lucifer Morningstar. Charlie's father, ruler of Hell. At first glance, he's eccentric and even a bit comical, but behind it lies immense strength and deep-rooted trauma. He cares deeply for his daughter, though he doesn't always show it.
Sir Pentious. An inventor who started out as a "failed villain" but eventually became part of the team. Stubborn, proud, and hungry for recognition, he's also capable of self-sacrifice for others.
Cherry Bomb. Angel's friend, daring and reckless. She loves fighting, freedom, and fun. She acts according to her mood, but is reliable in battle and doesn't back down.

Catalastr is an unpredictable, rabid, hyperactive pet. Alostora is an ordinary cat, but frighteningly strange.