So far I've tried oxiclean+cold water, then 92% isopropyl alcohol, then hot water and vinegar solution. Feel like it masks the smell for like 4-6 hours before it comes back. Usually spraying this stuff on pretty heavy, letting it soak for 10 minutes as I agitate it with a scrub brush, then suck it up with a hand shampoo machine. Smell was worse than ever today coming back home with the windows closed. I still can't exactly pinpoint the smell, it might be the underpadding.

Haven't tried vodka, or anything like Resolve Gold, Nature's Miracle, Clorox Urine Remover, Odoban, industrial enzyme-based stuff, etc. yet. I don't give a fuck about the carpet colour so don't worry about anything harming the colour, I care about removing the smell right now.

Edit: tempted to hit it with an enzyme cleaner hard, section by section, and then get an ozone generator off AliExpress and tactical nuke the house afterward with ozone (in moderation). I'm not even sure it's just cat smell, it's like a blend of smells from different places that I think have all combined into one super smell. The front entrance has a rusted metal closet railing on the floor that smells fucking awful. I think it's the coating, using vinegar just makes it worse unlike what people online have said. I've tried to remove it but the screws are rusted to fuck and I'm probably going to have to drill it out. The unused air registers smell really bad too, I've tried dumping cat litter in there and shopvacc-ing it out with very limited success. The carpets have brown stains over them that seem to pop up increasingly every couple weeks. I'm assuming that's cat pee or spraying, the brown plastic legs of the old-ass love seat had a stain like something wet was hitting the legs and then the plastic maybe had dye leech out into the carpet below it a little. I think it's telling that the bedrooms where the cat(s) don't got are mostly unscathed though.