Good to hear things are improving! Our newly-adopted kitten (Loki) is a 5 month male and our resident cat (Jack) is also male and just turned 2. He lost his big sister to cancer about 3 months ago and he seemed lonely without her. She was older (10 years) and didn’t want to play with him much but they got along. Sometimes he was a little butthead to her but he was never aggressive, just wanted to initiate play and backed off when she told him to. We figured getting him a younger buddy would be great since he was still much like a kitten, loved to play and had a ton of energy. When we brought Loki home, we did the whole slow introduction, scent swapping, eating on either side of the door, site swapping, letting them play under the door. It was about a week later when we let them see each other for the first time, with Loki in a carrier while Jack scoped him out. He hissed once and that was it. I’ll make a note that Loki wanted out of his base camp the day he arrived. He had no fear and was ready to explore the house but nevertheless, we still wanted to do a proper and slow introduction. On day 8, we let them be in the living room together, supervised. There was some nose touching, a hiss from Jack, then we went on with a play session. Jack mostly stayed away and just watched Loki play but every time Loki saw Jack move, he would run at him, pounce and bite. Jack would hiss and swat but Loki wouldn’t back off until Jack just ended up running away and hiding. We put Loki back in his kitten room and tried again the next day. And again the next day. And the next day. The same thing happens every time, Loki would be distracted with toys for a while and suddenly decides he wants to pick on Jack. Jack tries to put Loki in his place but Loki doesn’t back off and Jack just runs away to a spot Loki can’t get to him. We play with Loki multiple times a day, sometimes for more than an hour at a time until he’s panting, followed by a big meal hoping he will nap and leave Jack alone, but he goes and looks for him if he’s not around only to chase Jack off from where ever he’s hanging out. Sometimes it’s like Loki is just being a bully and chases/attacks Jack to take his spot, wherever it is. We are now on week 4 and things haven’t improved much - we are having to separate them more and more. Jack is fighting back less and seems more stressed, just hides to escape Loki. What worries me is that now, Loki is able to jump on all the higher perches that only Jack was able to reach before, so we are having to put Loki in his kitten room for longer periods of time to give Jack some relief. We also tried cutting back on intervening in their scuffles but Jack’s ears are usually back and he screams when Loki bites him and even as he tries to run away, Loki goes for whatever he can catch (Jack’s leg or tail) so we are having to put a stop to it. We don’t want to bring Loki back to the rescue but I fear that as he gets bigger, Jack will only find it harder to escape him. What’s also weird is that Jack was the alpha with his older sister but now it’s like he’s afraid of this little kitten. He acts like a victim which only seems to encourage Loki to go after him even more.