I have a question. Did you put any effort or thought into this character at all?
First, the history. Why were his parents trying to kill him? Did they receive a bounty on his head and were they desperate for money? Were they mentally unstable, and thus decided to murder him? Were they in withdrawl from some dangerous drug that seriously impaired their thinking process? Did he forget to take out the garbage and it was the last straw for them?
Next, why would they be "defenseless" if they were trying to kill him? I would suspect that one of them would have a gun or sword in hand... very few people attempt to choke someone to death or beat them to death with their bare hands. Some weapon would be necessary, even if it was only a kitchen knife or something. Also, why were swords lying around their house? Did his dad buy them to protect the family? Was the father a blacksmith and thus the swords came from the family forge? Were they heirlooms from the family's heritage? Even if they were any of the above, why wouldn't the parents have them in hand to try to kill poor Richerd? Unless they were in his possession personally, but where on earth did he GET them?
The next sentence is a jumble of words and doesn't even make sense. Following his double homicide, wouldn't he be arrested? Sentenced to death? Kicked off the damn island or something? Further, why would he even decide to kill half of Fishman Island? How do you just... DECIDE to kill half of an island's population? Besides, normally in such a situation, numbers would eventually prevail because of the army's obvious skill advantage over a ten year old randomly swinging swords. Even if the army didn't neutralize him, I'm sure the populace would have been able to take him down rather easily.
Further, Luffy has a bounty of 300,000,000 berris, and he has killed nobody. Why would a person who has killed half of an island have a bounty 1/300ths of his? Wouldn't he have something about the same size, or even just half or a quarter?
Next, his personality is flat. Flatter than a piece of paper. He's made of pure evil, simply because his parents tried to kill him when he was younger? He has no interests besides murder, killing, and gold? He hates EVERYONE? No exceptions? And how can someone who has to support themselves through rigorous combat and training be LAZY? His personality is not only flat, but it's contradictory.
His special ability makes no sense. No fish is capable of producing fire by rubbing its scales together, and the only character known to do something like that (Sanji) can only do that after an intense amount of movement in his leg and many years of training with a skilled teacher. Further you can never set "anything" on fire. You can't set water on fire, can you? Also try to give us a ballpark view of his strength level, because it would be nice if you could specify how strong he is.
Please try to clarify your abilities, because the descriptions are rather hard to read.
A side note: Fishman Island is not in the All Blue, it is in the Red Line.
Finally in this human centipede of problems, Fishman's Trust is an impossible move. He can't just "steal energy" or life force or whatever it is you want him to steal from someone. He has no devil fruit, and he can't do anything like that.