Lucy Gru is a (former) antagonist turned deuteragonist of Despicable Me 2, and the tritagonist of Despicable Me 3.
Lucy, although introduced as a serious and stoic woman, is generally very happy, enthusiastic, cheerful and perky, which is shown when she exclaims, "Yay!" after telling Gru that she's his new partner. She seemed to be quite alert at times when Gru tried to freeze her with his freeze ray, when she quickly countered this attack with her flamethrower. She is also very athletic and skilled in combat, demonstrated when knocked a tray of cupcakes and managed to strike every single one, with "a combination of jiu-jitsu, Krav Maga, Aztec warfare, and krumpin'!" although she flung the remainder of the cupcakes at Gru. She's also shown being a great athlete when she fights Eduardo's guard chicken, El Polito. She might also have some traits of jealousy when she noted Gru is on a date with Shannon and spied on them. Lucy is also very good at keeping cool in dangerous situations when she hijacked Gru whom is using his Freeze Ray. She also remained somewhat cheerful and calm when she was strapped to Eduardo's rocket, although in reality she was freaking out. She was impatient in traffic as seen when she is driving on the bridge and doesn't stop for anyone. She probably doesn't like music being on while driving as shown when she slapped Stuart's hand when he turns the radio on. In some points, Lucy was portrayed as attractive and a beautiful person, catching the eyes of Minions including Dave, Stuart and Tom. When Agnes met Lucy, it was clear that she noticed her beauty and asked her "Are you single?".
She zapped Gru with her electric lipstick taser and shoved him in her trunk.
She kidnapped Gru and brang him to Anti-Villain League.
She zapped Minions with electric lipstick taser when they tried to save Gru.
She destroyed all Gru's cupcakes, and beat up one of Minions (even though she didn't know that he's the real minion).
She spied on Gru's and Shannon's date.
She forced Margo to eat Nico's cheese, even though that she knew Margo didn't want to do that, because the cheese was annoying.
She was cruel to Nico when he revealed his true feelings for Margo.
She attemped to beat up Nico's mother when she was cruel to her and Margo because she was cruel to Nico.