Board Thread:Shadow Fight 2 Discussion/@comment-2601:147:8500:2740:E8A0:101D:186B:CA6F-20190316233602/@comment-31479589-20190317025740

There is actually a chance in each hit to be a Critical, although I don't know by how much. It seems to be not that high, but it's not very low either. There's also this rumor that Precision increase Critical chance, however I can't confirm this. At least for Shadow; some enemies with Precision on their gears seems to have their Critical chance increased.

Tl;dr: Yes, Critical is random too.