There's a lot of different ways to approach this. Are we excluding severe and extreme circumstances like being blind or quadriplegic? Are we only including immutable and permanent characteristics?
If so, I'm going with low IQ. Also I know you said besides autism, but honestly being low IQ is worse than being autistic in the sense that a mild to moderately autistic guy (NOT talking about chris-chan tier autism) with an average IQ will live a much better life than an NT guy with a low IQ. There are careers that pay well that autistic people could thrive in like programming. Low IQ people in 2025 are relegated to working low wage, menial jobs (that are usually stressful) for their entire lives.
I don't disagree with the people saying "poor", it's just "poor" in SOME circumstances can be temporary. Yes, I know there's no much room for upward mobility in this economy and most people end up in the same socioeconomic class as their parents or worse but in some cases you have a chance to escape poverty. Low IQ means escaping poverty is effectively impossible.
I actually thought about this for a while and I could make a tier list if anyone is interested.