Nick Diano

Name: Nick Diano
Age: 15
God Parent: hephaestus
Mortal Family: Alexander Diano(step dad) Mary diano(mom)
Years in Camp: 4
Brief History: Nick used to live in Colorado whith his familly, untill a monster attacked him when he was 10. He was forced to go to camp half blood where he would live. His mom said he would be safe their but he had no idea what she was talking about. After a couple of years at camp he got used to the fact that his father was a god and whenever he exited the camp he was in danger. He made friends at camp but he likes to be alone every now and again.
Physical Appearance: Nick is tall and has muscles. Usually he will wear a camp half blood t-shirt, but he will wear a whith t-shirt whith a black hoody sometimes. He alsoe wears jeans or swear pants. He has short brown hair. His eyes are a light green. He wears regular red nike sneakers. He is tan and has black hands from all his time in the forges.
personality: Nick is an exelent friend when you whant him to be, but if you make an enemy out of him you will regret it. He has extreme ADHD but he takes pills every day to controll it.
Fatal Flaw: he gets memory loss often, he forgets anything that happens whithin5 min. before it happend. if he where supposed to be battling like an earthborn or something and gets his memory loss he instantly forgets what he was doing and why he was doing it.
Talents: Like most hephaestus kids he is great whith creating things, but sometimes he will create something amazeing that no one else might be able to do (like once every month) but there is a 1 in 12 chancd that the thing he builds will actually work.
Weapons: he has a sword he made a while ago in the forges, he calls it venom strike becouse it sounds cool lol
Other: he is an all year camper

I'll assume by 'extreme ADHD' that you mean he's hyperactive. However, taking pills to control it is kindof against half-blood lore, since demigods often have ADHD (A focus disorder, not necessarily shown in being 'hyper' all the time.) and said ADHD is what helps them be so great in a fight, since their attention shifts often, allowing them to catch subtle movements in or before a fight.
I also wouldn't count ADHD as a personality trait, since that is present across multiple personalities.

Either way, the personality is too short. You really only described two traits: "Loyal and vengeful". If you need help, try considering this: What makes him loyal? Is he caring, or just stubborn. Why is he vengeful? Does he have trouble moving on? (Normally leading back to stubbornness, but not necessarily.) Does he have a violent temper? What sort of temperament does he have? If you want to tie in the forgetfulness better, is he normally scatter-brained? How is his focus?

That fatal flaw is interesting, and makes it rather incredible you have any long term memories at all, like your name... but it's not really a personallity short coming. If you really want that as part of your character, it would go in another area, possibly "Other". For your fatal flaw, look at your main personality traits, then think about on what would happen if you took one dominate trait and stretched it to its extreme.

So, work on fixing that.
If you need help, feel free to message me and I can help you work out the details, even if you're determined to keep the traits you have on there.