Regardless of the fate of the contractor, when Ai punishes an Asshole Victim who truly has it coming, it is always awesome.
When Ai fires an energy blast at Hone Onna and Ren after telling them to shut up for interrupting her attempts to subvert Tsugumi's decision
At the end of the first season, when Ai destroys the temple dedicated to the children from her village who, like her, were sacrificed to the gods (made by Sentarou to atone for his part in burying her alive), indicating that she got over her past and will finally move on.
There's also Ai basically saying "Screw it" and saving the life of the little boy that was the target of a contract in the ending of the second season because he reminded her of what she had to endure in life
Let's not forget Tsugumi's ultimate rejection of Ai's Mind Rape — telling her that no, she will not send her father Hajime to Hell.
When Takuma threatens to burn down the house of one of the people who victimized him and calls out an angry mob for their sins.
Just when you think poor Yuriko is going to be raped, Wanyuudo barrels down the dark street in his firey head form to protect her.