Mafia 56. Avatar: Invasion.

Or can the Mafia use more than two special actions per night?

I didn't specify it in the rules; I'll add it somewhere.

So, the ultimate ability might be wasted with a probability exceeding 50%.

That's the point. For example, in your Mafia game, Dimka's ultimate ability would have been useful. That is, a specific situation is needed.

The probability of disrupting an execution, the probability of protection.

Yes, it's a universal ability. There are many possibilities – it's up to the Mafia to guess what to use. Actually, I wanted to give Aang a different kind of mass killing ability, namely, to kill all players with a certain probability (then all these protections would be especially useful). But I decided that it was too much.
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Well, I don't know, what about the long-forgotten World War II? Or the Winner's proposal for a new Star Wars setting? I can dig around; I'm sure I'll find something, but I'm lazy.

Yes, I remember. And I remember about the zombies.
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The Mafia has the ability to send out several special actions. Possible night actions: kill + joint non-killing action; joint killing action + ordinary non-killing action; killing action + 2 ordinary actions.

This is how I wanted to handle the special actions, unless there are strong objections.