Sans has intangible attacks, and that shouldn't prevent Sans from manipulating his soul. I would say it purely comes down to whether or not Sans can kill Purple Guy before getting too tired to keep going. So how much can Purple Guy tank? Sans can easily kill an enhanced Frisk, who, in a far weaker state, was capable of tanking a 101,339,049 joule, or 24.22 kilograms of TNT explosion, and suffered absolutely zero injury. Alongside much better Danmaku than what Purple Guy can use, not to mention that each attack would hold at least 101,339,049 joules, and have soul hax. Also keep in mind that base Purple Guy is 9-B. Even if we used the peak of 9-B for him, which I'd guess is a big highball, Sans would have almost a 5x advantage in AP at a bare minimum, which is nearly enough to one shot. Hell, if we used the bare minimum of 9-B, the difference would be 6,755 times, which would be enough to kill Purple Guy about 900 times over from one hit. While I don't doubt that Purple Guy is significantly above the bare minimum, I do highly doubt that he's at the peak of 9-B. I would guess that Sans can almost certainly one shot base Purple Guy, actually. I don't know how much the bytes and chips can increase his statistics, but I think Sans would be able to kill him, before he gets too tired, in any case.