I deserve to hurt

About 2 months ago I adopted a 3 year old cat from my local shelter. He’s super sweet but does bite a bit when playing but when it came to my other 2 cats, he’s was increasingly aggressive. I tried enrichment toys, calming products, and had him evaluated by a vet who prescribed medication, but unfortunately nothing helped. One of my older cats became so stressed she had to be hospitalized, i was at the point where I couldn't keep him safely. I’ve tried finding a new home myself but haven’t had success. Ive asked people at work, my friends, I posted on fb, nextdoor and other sites but had no success. I called the shelter that i got him from but they couldnt take him back. I emailed and called several rescues and other shelters but they either never got back to me or they were full and couldnt take him in. I didnt know what to do. The thing that broke was when he attacked my other cat and I had to separate them. She looked so scared and hid in a corner. It broke my heart. I left him out closed the door and I cried. Later I heard him meowing close by but I couldnt open the door. A neighbor had found him in my apartment and was knocking at different doors to see who's cat it was but I pretended I wasn't home. Im not sure if the neighbor still has him or took him somewhere or what. I love my other 2 cats and it broke my heart seeing them so scared and hurt. I didnt know what else to do. The guilt is eating me alive and I deserve all the pain I'm in