I'd say roughly 10% of Danny Phantom fics are great, 20% are good to mid, and the last 70% of Danny Phantom fics are bad or WTF because they all work under the same 3 variations.
Abused Danny Phantom: I don't know what it is but it's horrific that many Danny Phantom stories revolve around Danny getting abused simple to fit the writers narrative. It's not even from his ghost fights, they have everyone from the students/teachers at his school, his friends, and his family physically and emotionally abuse him and results in him becoming ultra emo, turning his back on humanity, or become some whimpering dog who can't speak.
To give an example of one of the worst ones I know, it was a crossover story with Marvel in which Danny is abused by everyone he knows (and it goes into detail) and becomes emotionally scared and mute, to which Vlad Plasmius (His arch enemy!) show up and save him. Then moves him to New York city so Danny could run into Peter Parker/Spider-Man so the later could help build him back up and they could have a gay relationship, with Loki coming out of nowhere and being a "mother figure" for them...
I don't how much cocaine you need to snort to even write something like this but people clearly are inhaling some crazy shit to like this stuff.
Run Away/Betrayed Danny Phantom: Now this tactic lines close to the abused Danny Phantom method but is different in some ways. It's either...
1. Danny's parents find out he's half ghost and he runs away because they attack him. This method while unique the first time is one that is done to death by so many others and thus isn't good because it only serves to move Danny out of the Danny Phantom setting to wherever the writer wants him to be. It's boring.
2. His family and friends betray him to the Guys in White and either Clockwork shows up and saves him (usually killing everyone else brutally while doing so) or they capture him and run experiments on him (this one leans into the abused Danny Phantom stuff)
Ghost King Danny: This is one used consistently when trying to make Danny stronger, not only does it break all forms of logic but it's just falls flat in terms of story. Regardless of how strong you think Danny Phantom is or isn't, he is not king material. They make a 14 year old boy king of an entire universe of over a million entities who'd floor his ass if any group of them decided to team up. It's simply something that's not done well.
I think what's worse is the stuff I'm talking about applies to the fanfiction, I just used Danny Phantom as an example but I've seen shit like this before and it makes you wonder why people don't think before they write. Heck I like the Loud House but the fanfiction is another example of having some messed up shit, such as stories where Lincoln is heavily abused by his sisters to the point were he's hospitalized, and let's not forget the weirdos who do all those incest fics with him and his sisters... (these people need help). People already talked about Naruto fanfiction in this thread so I don't need to go into that.