Full disclosure, I've never been as big a Sonny fan as the days of Brenda-Sonny version 1.0. His character has undergone much needed repair under the current regime admittedly. Still, at his core, he's a bipolar, serial monogamist (7 marriages and 3 baby mamas - without as much overlap as you'd think), mob boss, with a madonna-whore complex. His saving graces, for those who see any, are his sense of honor and his commitment to his children.
First there's Michael, Sonny's adopted son. Though the middle child in age, Michael was named after Sonny and was the first (and really only) kid, Sonny raised fully - except for those month/years when Michael was in the coma. Despite Sonny giving his word that he wouldn't hurt Michael's biodad AJ, Sonny shot AJ, who later died from his injuries. No one suspects Sonny, and he is racked with guilt. But Michael feels the loss of the father he was only beginning to know and the uncertainty from being the one charged with making AJ's final medical decisions. Though a woman's life was in danger at the time of the incident, Sonny had diffused the situation. Yeah, yeah, yeah he thought AJ killed Connie, but still - he murdered his favorite kid's biodad and then had the temerity to go to the funeral!
Then there's Morgan, Sonny's 3rd or 4th favorite child (of four). Sonny, on a non-medicated bender had already destroyed Morgan's ill-advised marriage to Kiki. But now that Morgan has found love again - with Kiki's mother, Ava - what does Sonny do? He has sex with Ava. At AJ's funeral. In the Quartermaine crypt! Morgan, stumbled upon them shortly after the disgusting deed and yelled, mostly at his father, about his hypocrisy. At one point screaming, "You don't even like her!" True, but if only Morgan knew, that's how Sonny and Carly first hooked up.
Sonny happens to be in a committed relationship, as in living together and sleeping with, the mother of his oldest son, Dante - who chronologically, as it turns out, was the last kid to come into Sonny's life. Olivia was literally wringing her hands across town, worrying about Sonny's mental health, while he was having crypt sex with his son's girlfriend - the woman Morgan confessed to Sonny was his "reason for breathing."
The above would be a perfectly suitable trifecta of parenting fails, but I'd be remiss if I didn't give an honorable mention to Cristina. Crissy is the only girl in the bunch (currently off the show and uncast). Her mom, Alexis, was wise enough to keep her away from Sonny for most of her younger years. Alexis is Sonny's lawyer and has emphatically stated she wants no part of his criminal activities. That didn't stop Sonny from trying to low-key pimp Alexis out to his competitor Julian, to see if Alexis could sweet talk - or pillow talk, some secrets out of the figurehead of the Jerome Crime Family. Granted, Alexis didn't mind so much as she and has had mad crazy chemistry with Julian-Derek-Julian from jump.
Sonny has had larger failings against his children - Michael getting shot by a bullet meant for Sonny, shooting Dante, shooting Carly while she was giving birth to Morgan --- but those were spread out. 2014 is starting off as a banner year of parenting fails for Michael "Sonny" Corinthos. There's no way any other TV dad can catch him at this pace.