this would be one way...
=IF(COUNTIF(C20:G20,"complete")>=5,"Complete",IF(AND(COUNTIF(C20:G20,"complete")<5,COUNTIF(C20:G20,"complete")>=1),"Some",IF(COUNTIF(C20:G20,"complete")=0,"None","")))
or if you have no other options this shorter version...
=IF(COUNTIF(C20:G20,"complete")>=5,"Complete",IF(AND(COUNTIF(C20:G20,"complete")<5,COUNTIF(C20:G20,"complete")>=1),"Some","None"))