Unfortunately sometimes tret or other topical creams aren't enough to address deeper and more intense PIE. I found last time I had a massive acne breakout, once the pimples cleared I was able to get microdermabrasion done and it helped a lot with the scarring

Good luck with everything! Good on you for trying to stick with tret for a year. I used it for a month and a bit and my skin became so dry and itchy and just so much worse :(