Pantera is a member of the Tomaso Famiglia. She apparently tries to kill Longchamp very frequently. Her weapon of choice is bladed pinwheels. Longchamp only thinks she's kidding around in her attempts to kill him, however, and dodges her attacks by instinct. When Tsuna asked Mangusta if something happened between them, he nervously refused to comment, implying that something indeed happened (though what happened exactly was never stated).
Though the chapters don't continue with Longchamp in view and the anime emits the family due to Longchamp's unpopularity, it is believed that Pantera harbors a crush on Longchamp. The attempts at murder are speculated to be from anger due to him solely dating women who are only his form of beauty.