Which is the best high performance processor among the options below? Intel i3 Pentium AMD A9 Intel i7



That depends on WHICH model among those series you listed, we are talking about.

A new Coffee lake i3 (8th Gen) for example might probably outperform an older Sandy bridge (2nd Gen) i7. Specific model numbers would be necessary in order to say what might be better than something else. Generally speaking, none of the A series AMD processors were much good for anything beyond internet browsing.

Older i3's were not very good either. Newer i3's are pretty capable and the i5's and i7's have generally been the work horses of each generation so for any gen, it's i7 is usually the best mainstream consumer CPU from that family.

An older i7 however might have a hard time beating a newer, especially when there are several generations between them, i3 or i5.

Then you have Ryzen, which are very competitive as well, from AMD. Any Ryzen 5 or Ryzen 7 is going to be a fairly decent performer no matter what you stack it up against, if it's going in a gaming machine, and maybe a better choice for productivity machines.