need your help, I have an M2-ATX supply that I blew.
I switched from the positive and negative so burned a component of plaque present in the image.
need to know what is the reference component in order to try to repair burned.
From the pic & above it seems it is a reverse-biased to absorb negative transients - which it did and blew.
Once that let go, the other reverse biased junctions would have fried. That means transistors in chips etc. IOW - as BigK wrote, a few else's may have burned.
If only the (reverse biased) diode blew, the PSU will work without it.
It would be any power diode - not critical; ideally the equivalent to IN4007 or 4007s etc.
It isn't a reverse polarity protection diode (unless it coincidentally happened to be faulty - ie, a short).