Grandma Agnes is the mother of Eileen O'Neal and grandmother of Kenny, Jimmy and Shannon O'Neal. She first appeared in the episode The Real Grandma. Agnes is a racist, bigoted, homophobic, die-hard Catholic fanatic.
Agnes is the mother of Eileen and Gary. Ever since she was born, Agnes had always treated Eileen like she was worthless and could never amount to what she wanted her to be. She blames her for all of her problems and is always seeing her as a disappointment. Eileen has seeked her approval, throughout her entire like, but has never gained it. At the point of her life, where she has become a mother herself, Eileen has given up, and has finally learned to just accept that.
In The Real Lent, Eileen mentioned "grandma" in dialogue, saying that she used to have a children's book depicting very graphic pictures of tortured and bleeding saints that she'd read to Jimmy, giving him nightmares. It's very likely that this grandma was Agnes.
In The Real Grandma, she came by the O'Neal house for a surprise visit. Due to her being unannounced, the family was freaking out, mostly because Kenny had to hide his sexuality from her and Pat and Eileen needed to hid their divorce from her. Kenny wasn't going to let Anges torture him, and so he went straight out and told her that he was gay, presenting it to her on a cake. Agnes fainted in shock because of this and when she recovered, she was very disrespectful toward him for it, and even tried having him sent to a camp. Eileen was in partial agreement with this for a while, so she allowed this. However, she eventually took it too far, by telling Kenny that he was "broken" and that he didn't care what God thought about him. This was too much negative criticism for Kenny, even for Eileen, and she had finally told her to stop. Eileen revealed that she and Pat were getting a divorce and that they didn't care what she thought. Agnes continued to be a horrible person, so they put her in the car, and drove her to Uncle Gary's house, where they would leave her. Gary was a relative of theirs that got married to a Hinduist, so this was going to spark a lot of anger from Agnes. With Agnes off their hands, they were free to be themselves again, and so far, Agnes is probably still with Gary and his wife, torturing them both.