Superhero Origins Usually Have This Trope
Batman's parents are a good example of "throwaway" characters who get used for the development of our main hero.
Without their death, there would be no Batman. Bruce Wayne might still have a strong sense of justice and desire to help people as he grows up, but he would not be nearly as motivated to fight crime.
Most versions of Thomas and Martha Wayne get minimal characterization other than the bare essentials and a few flashbacks. They were good people, good parents, and they left Bruce a hefty fortune with their passing.
So what makes their deaths compelling? The impact their passing had on Bruce Wayne.
Without his parents, he's hurt, scared, and alone, but any good version of Batman is not motivated by hate, fear, or pain. Rather than fighting crime out of deep hatred, he should be helping people because he simply cares. He does not want any child to have to go through the same pain he did.
Because of that, his motivation is not solely born from the parents he lost, but also born from one of his key defining character traits, helping people in need.
Even if the point of the story is that your character is consumed by a need for revenge, the loss should not be their only motivator. The other half of the equation is the needs and desires of the MC.
Perhaps they have a strong sense of justice. Seeing a criminal go unpunished is unacceptable, and that becomes their driving motivator. Maybe they were a reckless hothead from the start, so seeing the death of the only person they loved is enough to push them over the deep end for real.
Or they could be motivated by a deep care for humanity. The MC isn't doing this because they hate the people involved, but because they refuse to let anyone else feel the pain they are feeling. If that means hunting the bad guys down herself, then so be it.
One problem I often see with revenge stories is that people often linger so much on the tragedy they never let the real character shine through. Batman would not exist without his parents' death, but that's not all he is. He's also smart, caring, and a master of the shadows. While being a caped crusader is hardly a healthy coping mechanism, he sees it as doing his part in helping the community. He grew and learned from this tragedy, he did not let it define him.
Sometimes in revenge plots, characters will have a "Woe is me" mentality where they get so absorbed by their pain that they feel like they're the only person who feels pain.
"My backstory is so tragic. No one could ever understand my pain or the depths of my blackened soul."
This is a big gripe I have with many versions of Batman, where they make him a bit too mopy and brooding. Even happy-go-lucky Superman lost both parents and his whole homeworld, but trauma is not a competition, and it never should be treated as such.
Avoid having your character become so self-pitying that they downplay the feelings of others.
Lastly, avoid painting the tragic backstory as an excuse.
A common tactic for protagonists is to point at their past trauma as a justification for any misdeeds they may commit. Example:
"You killed my father, so I am morally justified in murdering your entire criminal syndicate," the MC says.
"Even my loyal minions who have no idea who your father was and were only following orders?" The villain says. "Most of them are just here because they're poor, in debt, and need to feed their starving families. Their worst crimes were petty theft. You murdered all of them?"
"Yep, but they were evil, and I'm good. I have a tragic past. So it's okay I lined the streets with corpses," the MC said confidently.
"I see," the villain says. "You know, I have a tragic past too. Lost my dog Rex to my evil neighbor Ken. So I started a decade-long war, killing thousands, just so I could get even with him."
"That's so tragic," the MC says, "I get it. You're just like me. You're fully redeemable. Let's be friends."
The above example is a terrible trope in revenge fiction. The MC lost someone so they mow through countless faceless grunts to get what they want, even if those grunts are mostly innocent. Either have the grunts be equally as bad as the main villain, complicit in the murder, or make it clear this is not a hero but an antihero/villain protagonist, because heroes do not kill innocents.
Another terrible trope is absolving the villain of wrongdoing because of a tragic past, or just deciding to spare them because of it.
Imagine slaughtering countless faceless grunts to the point your hands are stained with blood, getting to the end of it all to finally face your parent's killer and going, "Nah, they have a tragic past. I can't kill them! Then I'd be a monster."
It's a common trope and it drives me off the wall. Even if the MC wants revenge, they should still have standards.
A realistic mentality would be, "I'm after my father's killer. I'm not here to hurt innocent people. Get out of my way or I'll have to use force."
A bad mentality is, "I'm after my father's killer. I'll slaughter anyone in my path just for looking at me funny."