Both were complete losers and abusers. You can bet that Barbara Healy was physically abusive to her kids, especially when they were younger. She and Fisher were both pitifully pathetic people. Fisher hid his better though. He didn't come across as an abuser. I see how he slipped under Roseanne's radar. Barbara Healy didn't even try to hide hers. She hit David right in front of Darlene. Then both apologized and tried to make it all about them.

They definitely were physically abuse. We saw Mrs. Healy slap David, and we know Fisher hit Jackie. Glad both David and Jackie were able to remove themselves from those losers.

Both characters were absolute bottom-tier human beings who used manipulation and violence to exert control, representing two different but equally "pathetic" faces of abuse.

Barbara Healy: The Overt Narcissist
Barbara was a textbook unstable, alcoholic abuser who barely maintained a facade of normalcy.

The Blatant Slap: As you noted, she slapped David right in front of Darlene—a move so bold it signaled she felt entirely entitled to use physical force to silence her children.

Victim-Playing: Her "apology" was indeed a classic manipulation tactic. By making the situation about her own stress or "failures," she forced David into the role of the caretaker, a cycle that likely defined his entire childhood.

Legacy of Trauma: Fans have long speculated that Barbara’s abuse was the primary reason Mark and David's father left and took the sisters—he likely viewed the boys as "tough enough" to handle her while he "saved" the girls.

Fisher: The Stealth Predator
Fisher was arguably more dangerous because he was a "chameleon" who successfully duped the entire Conner family for months.

Calculated Isolation: Long before the physical violence, Fisher engaged in "pathetic" psychological warfare—convincing Jackie to quit therapy and isolating her from Roseanne so there would be no one to witness his behavior.

The Mask Slips: His true nature only peaked through during the poker game with Dan, where he lost his temper over a low-stakes hand. That "sore loser" energy was the precursor to the brutal physical violence Darlene eventually discovered.

Cowardice: In the end, he was a coward. He pressed charges against Dan for the beating but eventually dropped them in a desperate, pathetic attempt to manipulate Jackie back into the relationship.

The show’s writers used these two characters to highlight how abuse can be either a loud, public explosion (Barbara) or a quiet, slow-burning trap (Fisher). Both were, as you said, "pitifully pathetic," and their exits from the show were some of the most satisfying moments for long-time viewers.