Lenny Potts is responsible for everything that happened
Had he not gave Danny those confession tapes of his siblings lying to the cops to cover up for their daddy beating the shit out of him, he wouldn't have snapped and went on some revenge plot. He kept listening to those tapes throughout season 1, almost like he was using them as motivation to keep hating them.
Pretty much everything Danny did to hurt his family in season 1 was because he heard those tapes. Its just funny to me Potts never seemed to feel the least bit guilty about it either, he stirred up the hornets nest and walked away feeling guilt free.
He blamed himself for not helping Danny back when it happened, so he felt like it was some form of redemption by giving Danny those tapes. How exactly was that redemption or how exactly did giving Danny those tapes help anything at all? All it did was piss Danny off and motivate him to get revenge on them.
He gave those tapes to Danny knowing full well it wouldn't lead to anything good.