The Queen of Spades is dangerous because she can help someone and still be setting them up.
Regina Depas has her own soldiers and her own claim to Wonderland. But a lot of her influence comes from getting involved in somebody else's situation before they understand what she wants out of it. Alice's struggle with the Jabberwocky is a good example. Spades assists her, but that assistance comes with an agenda. Alice needs to survive. The Queen is thinking about what Alice's survival can do for her.
That's a really important distinction in this setting. If you're trapped in Wonderland, someone offering help is going to matter. You don't have the luxury of knowing everybody's history or checking where their loyalties are. You have whatever information they give you, and they may know a lot more about your situation than you do.
Spades also reaches outside Wonderland. In Call of Wonderland, she appears as a librarian and puts a book in Julie Sands' hands. It is a much quieter way to become involved in somebody's life than arriving with an army, which makes it worth paying attention to alongside the more obvious displays of power.
Her rivalry with Hearts develops into a major part of the ongoing series. While Calie is trying to protect Violet, Spades is building the strength to seize control of the realm. These are different problems happening at the same time, and the Liddles don't get to deal with their family situation in isolation from what the rulers are doing.
Spades has shadow-based magic as well as the soldiers under her command. That fits the way she operates, but the bigger danger is her willingness to use other people to move her plans forward. You have to look at what a helpful act sets in motion, not just whether it helped in that moment.
By Wonderland #24, that interference has brought Calie to the point of gathering allies and heading toward Spades directly. Regina has been involved in the trouble around both Calie and Violet, and now the people affected are coming for her. It's a confrontation with a history behind it, reaching back through choices the Queen made well before that moment.
The Queen of Spades is dangerous because she can help someone and still be setting them up.
· Comics / Grimm Universe