Andy was used to apologizing. From mediocre grades, trouble at school, failed attempts at socializing, and recently his abilities. At school eventually he got tired of it and tried to stick to the sidelines and shadows. Getting through it doing just enough to get through the day and letting himself be pushed around. It was better this way then to draw any focus on to him.
When his parents confronted him about it Andy apologized and wanted it to be over. When the kids who antagonized him found him at the dance he thought if he tried to apologize they'd probably just give him a relatively quick beat down or just toss his around.
When he ruined his family's normal life he was sorry. When because of him Lauren revealed her secret he felt guilty for his comments he had made for so long.
When he couldn't save his dad he was sorry for bringing all of this on his family. When he saw Sonya die because Lauren and him didn't demonstrate Fenris soon enough he was guilty. She was dead because of him.
Jace and Campbell wouldn't have gone after the Underground or after the Strucker family if he wasn't such a easy target if he wasn't weak. If he could have just sucked it up and stayed home.
When he made that tremor and sent the people that helped him nearly to the floor he felt guilty. It was nothing new to them. He cared about all of them but seeing all of them like that hurt even worse.
He kept messing things up or not doing enough. He was helping people but he should do more. He caused all of this and was sorry. The Hellfire Club couldn't change the guilt he felt but maybe he could actually do something.