GARDEN CITY — It was payback time for Great Bend’s football team.The Panthers played giant killer by upsetting Western Athletic Conference champion Garden City 20-7 to spoil the Buffaloes’ Senior Night Friday. Even Thunder, a buffalo from West Texas A&M, failed to inspire the Buffaloes with pregame and halftime jaunts. The victory avenged a 21-14 overtime loss to the Buffaloes last year.Great Bend (5-3, 2-2 WAC) qualifies as the fifth western seed and plays Goddard Eisenhower (3-5) in a home 5A playoff game Oct. 27.