This has been done before, I've already gone over why Sans wins this in another thread so I'll just talk about it again here.
To begin with, the massive AP advantage Sans has. Sans is capable of harming LVL 19 presumably high DT Frisk, who scales massively above their LVL 1 presumably no DT Pacifist Route self, who can effortlessly tank a 101,339,049 joule explosion with no damage. That is 6,755 times the bare minimum of Wall level, the tier that base Purple Guy is listed in. While I don't doubt that Purple Guy is significantly above the bare minimum of Wall level, especially when enhanced, it would still be about a 5x AP gap assuming he was at the peak of it. Regardless, we can assume that Sans would kill Purple Guy very quickly if he landed one decent attack on him.
While it is possible for Purple Guy to kill Sans if Sans gets tired enough, there's no reason to assume Purple Guy would be able to do that in time, given how Sans would fight him in character. He would throw him to the ground using telekinesis, which PG can't avoid, then pierce him with a row of bones, something PG wouldn't see coming. And even if he survived that, I highly doubt he could survive the remainder of Sans' first attack. It's a stretch to not even say that Sans stomps PG, as he would almost certainly kill PG before PG can do anything to kill Sans.