Here is a list of teams that played Portsmouth either before the Final 4 or in the regular season and won the state title:
1925: Springfield beats PHS in the regional finals
1926: Zanesville beats PHS in the regional finals
1950: Springfield beats PHS in the regular season
1952: Middletown beats PHS in the regional semifinals
1953: Middletown loses to PHS in the regular season
1954: Hamilton beats PHS in the regional finals
1956: Middletown beats PHS in the regional semifinals
1957: Middletown beats PHS in the regular season
1961: Ashland(KY) beats PHS in the regular season
1963: Columbus East beats PHS in the regional semifinals
1964: Dayton Belmont beats PHS in the regular season
1987: Dayton Dunbar loses to PHS in the regular season
2008: Chillicothe beats PHS in the regular season
Note: In 1925 and 1926, the regional finals were actually in the Sweet 16 state tournament.