Cat viciously attacks me for no point?

I've had this black cat since last summer, we found him outside of my work surrounded by the bushes. He was pretty small, about 5 months old. It be really cold that night and rainy. We took him home, and care for him, and then in November we got another cat, which be a Tabby Point Siamese. Then things happened and my whole family be forced to move in with my grandparents who had a cat already. Everything be fine until my black cat started fighting with my Siamese cat. I'd do everything to try to separate them like spray them next to water, clap my hands, and shout at them, and eventually they would stop. The fights started getting pretty distasteful, and I had to take my black cat to the vet to heal a huge infection due to a mark. After I separated the two (I always grabbed my Siamese cat and put him in my room) my black cat would viciously attack me. At first, it started beside my foot, then my leg, and one I was just petting him, and we be being really friendly toward each other and all of a sudden in need warning, he turned on me and bit and clawed the hell out of my arm. It was so deep, it be to the muscle and nearly required stitches.

The other night, my black cat and siamese cat got into a really nasty conflict, and I ran up to them, stomping and making noise. My siamese cat frantically tried to get absent, and then they stopped, and just stood there facing respectively other. I did what I always did, I separated the two and put the siamese cat in my room. I left my bedroom door undo on accident, and put the cat on my bed, and all of a sudden my black cat runs into my room, CLIMBS UP MY BACK and hisses at me. He is a 14 pound cat, and there is just about any fat on him so he is huge. His claws were dug in so thoughtful that it caused bruises around the marks.

My dad threw him outside for the first time ever since we get him. He hasn't been back since. Recently he had be acting up. He knocked over the christmas tree, attacking the other cats, squatted in the middle of the floor and peed right in front of us, RIGHT after the litter box be cleaned, climbing on everything, and had been attacking me for no reason. We have been talking about getting rid of him, because his behavioral issues be completely out of control.

It just breaks my heart because I loved and cared for that cat, and never abused him contained by any way. I tried loving them both equally, and spending time with each one of them. I meditate that the black cat wanted the attention all for himself, and got green and started attacking both me and my Siamese cat. But I don't know. I feel guilty, maybe I should have given my black cat more attention, I don't know. But I don't assume he's going to come back. :(
It sounds similar to you're cats need to be fixed if they arnt. If cat's have they're "parts" they receive territorial and will fight and if their is a female contained by "heat" then they get even more aggressive. Take him to the vet and if they arnt fixed hold them fixed and if they are then something is wrong and they may need medical attention

Also never simply push inbetween them if you know they fight get a squirt bottle crowd it with water and squirt them to seperate not a supersoaker just something to startle them and acquire them distracted from the fighting mode. If you get in the course it won't stop them just slow them down or irratate them don't intervene unless you're 100% sure of how they will react.

First things first bring them to the vet for their own health.
Jealousy!
Answers:    how long ago was the move as a posed to his behavioral changes? the judgment I ask is often when a cats day 2 day life-style change and they don't know why, it can send their little minds into a crazed state. until they adjust to the changes all kind of hell can break loose. Kinda like what you explained ,potty issue ,change in play ,and lashing out at owners. Its not that they don't love you any more or that they don't want you cuz they really do. Now more then ever ! I guess in my eyes throwing him out is not the answer.Tiring to understand what he is going through and helping him through these change would help tighten the bond between you and your cat . See when you put the other cat in your room its telling your black cat hes 2nd best and surrounded by his eyes he came FIRST . Your room is where your sent is the strongest and being you save him from the cold rainy night he felt a stronger bond beside you ! Know your poor kitty is back out their where he was save from,( by you) when he was small, this could lead to more problems in this cats go He most likely wont trust people any more . If I where you I would travel out side and leave food # 1 plus call for him , to see if he will come domestic , if a week goes by and the food has no loose change in the bowl and he doesn't come home then I guess im sorry for your lose -ski- You should try to clear this right for you and your cat ! poor kitty needs you .
sounds similar to the cat has jeolousy issues if he does come back find him a domestic where he will be the only cat there till he dies it will be the best for him also whether he doesnt dont worry about it cats are survivors they adapt natually as strays unlike dogs
Sounds like your cat is a bit jealous.
When my cat does the "kneading" point, he also does this little reverse jiggle.  What does THAT suggest? ?   I've name my cat Dr. Evie Montgomery IV. She certainly doesn't hold a doctorate, so will she return with surrounded by trouble?   Cat spraying problem...?   How do I stop my cats from chewing me out of house and domestic?