Which Cincinnati Red has had the most success hitting against the Giants? In 141 plate appearances over nine seasons, Ken Griffey, Jr. hit .313/.436/.670 for an OPS of 1.095 (there’s some rounding involved there). The full table is here.
Griffey’s OPS during his time with the Reds was .873, and so he also has the largest difference between his OPS generally against the league and his OPS against the Giants (1.095 – .873 = .222). Griffey’s BAbip, however, was .294, when about .300 is average, so Griffey was actually a little unlucky against the Giants and should have put up slightly better numbers against the Giants but for that poor luck. Other Reds of note include Hal Morris, who almost matches Griffey against the Giants, with an OPS of 1.016 compared to his league-wide OPS of .810.
And George Foster? He hit for an .866 OPS as a Red, but only had an .851 OPS against his former team. Still doesn’t come close to making up for that trade, though.