Ive blown one up pretty bad before too. The piston was melted on top and there was quite abit of shrapnel everywhere too. Turned out to be lean jetting and extremely cold air temp. But man, there looks to be quite a bit of dirt residue on the crank, inside of piston and cases in your pictures. Did you knock that in there while pulling it apart or could have you been sucking in dirt to cause that catastrophe ? I think Cbmoor is mistaken, that appears to be intake side of the piston right where dirt would get sucked in first and begin the damage process. Ive seen plenty blown up by a poor intake and aged piston, that sure looks like one.
Whatever the cause may be, I agree with others, if budget allows...complete rebuild if you want it to run strong and last.
good luck