Some things are just hard to get right without being there. There's a ton of heavy black carbon inside the outer shell, deposits on the ground strap, and it appears there is oil on the outside of the shell on the second plug. It does look like oil burning. It also looks like the plugs might be the wrong heat range for this engine although that's hard to imagine looking at where the center electrode is in relation to the shell. The scary part is all the little chunks or balls stuck to the center electrode on the wet plug. Every time I've seen that it's been accompanied by melted piston parts. That line on the center electrode of the first plug, where it's dark above and light below, looks like the "timing line" you sometimes see on the center porcelain. If it is then the timing's too far advanced by quite a few degrees. And it needs fuel...

Is there a lead substitute additive being used? I see orange spots on one of the plugs. That additive can leave deposits on the ground side as well although it still looks like heavy oil burning on the one cylinder.

If the engine's damaged you'll get the same story pretty fast with a new set of plugs.

Is the engine owner going to try and add a knock sensor? Can we do leakdown tests?